LPs Versus CDs: An Unnecessary (and Often Annoyingly Ignorant) Debate

I am truly at a loss as to why we are still arguing about this, but we somehow still are! (See “Retailers Giving Vinyl Records Another Spin.”) Here is the quick answer: digital-audio techniques and media can capture and reproduce sonic events far more faithfully than any analogue technique and medium. Note that the focus of the above statement is fidelity not preference, a distinction that most “LPs versus CDs” debates wrongly blur.

Old news

More than twenty years have gone by since the first time CD sales surpassed those of LPs, and several highly qualified acousticians and engineers have since weighed in on the LPs-versus-CDs topic, outlining in numerous books, scholarly journal articles, and presentations the mathematical, acoustical, signal-processing, and perceptual issues involved. (See the relevant, well-written article on Wikipedia for a partial bibliography. See, also, an intelligent talk on the topic by Princeton University’s Paul Lansky.) Some of these experts have also sent relevant letters to the popular press or have published blogs and other online resources. (See this post by analog-integrated-circuit designer Mike Demler.)

Still, self-proclaimed “experts” and die-hard lovers of popular myths, who seem to approach knowledge almost exclusively through what C. S. Peirce, in the 19th century, called “the method of tenacity” (holding on to one’s already established beliefs at all cost), insist on keeping the analogue-versus-digital-sound debate alive. See, for example, this thread on Audiokarma.org’s discussion forum, which includes a typical example of the types of arguments used by LP advocates: “I know vinyl is better because… it just is” (emphasis in the original!).

I will not waste any time here repeating in detail the arguments for the superior audio fidelity of CDs versus LPs. Interested readers can find more information through a relevant Google search, assuming they know how to weed through the returned results and evaluate Internet resources. (e.g. Does the author identify him/herself? What are his/her credentials? Are the arguments supported by references to credible, peer-reviewed sources? Are the sources of information properly cited? etc.)

I will simply outline the inherent and unsurpassable limitations of analog media, such as vinyl LPs, and highlight an important distinction between fidelity and preference that seems to be overlooked in digital-versus-analog debates.

Limitations of LPs

The mechanical nature of sound-signal capture and reproduction in LPs and the associated issues of inertia, momentum, and interference impose frequency and dynamic response limits (i.e. limits in both the range and fineness by which a signal’s frequency and amplitude content can be captured and reproduced without interfering with adjacent signals) that constitute an unavoidable fidelity bottleneck within the medium. CDs completely bypass these issues thanks to optical methods of sound-signal capture and reproduction, assuming appropriate digitization (sampling-rate and bit-depth choice), storage (CD-surface and surface-coating choice), and handling (CD-surface protection during use to minimize the need for digital error correction).

Fidelity versus preference

Advocates of LPs and other analog sound media often cite the analog sound’s greater “warmth,” “smoothness,” and “fullness” as the main reasons for choosing analog over digital. Interestingly, these subjective sound-quality characteristics are related to acoustic side effects imposed on live, sonic events by the analog media themselves. Preference for such sonic qualities may be based on familiarity and habit (having grown up listening to music exclusively through analogue media, showing a conditioned preference towards the “familiar”) or may constitute a conscious aesthetic choice (intentionally altering a sonic event, through the sound-quality distortions introduced by analog media, to achieve a given aesthetic result). Regardless of the reasons behind some listeners’ preference for the sound-quality distortions introduced by analog media, the fact is that the sound quality carried by such media is exactly that: distorted. Preference for analog over digital and the other way around occupies an inherently subjective, gray area, and discussions on it can and will continue. However, when it comes to sound fidelity (how accurately an acoustic vibration is represented by a sound signal) it’s just black and white, with digital coming out the clear and undisputable winner.

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Libx

Libx is a Web 2.0 tool that connects you to the university library while exploring the web. Available for Firefox and Internet Explorer, this plug-in is customized especially for DePaul and pops a handy little search bar across the top of your browser window, so you can quickly and easily search the library catalog or check on whether the library has the journal you need online or in print.

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Even better, when searching for titles from Amazon, Barnes & Noble, or many other sites, you will see a little DePaul icon next to the book title allowing you to see if it is available in the DePaul Library.

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In addition, you can highlight any word or phrase in a web page and right-click to search the library catalog for that item or drag-and-drop onto the ‘Scholar’ button in the toolbar to generate a search in Google Scholar.

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Speaking of Google Scholar, if you set your scholar preferences to include library links from DePaul,

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your scholar results will have ‘find full text’ buttons.

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Now you are never more than a click or two away from finding out whether the library has what you’re looking for.

Give it a try!

For Firefox:
http://libx.org/editions/download.php?edition=CD98EF7E

For Internet Explorer:
http://libx.org/editions/CD/98/CD98EF7E/libx-CD98EF7E.exe

(More general information at: http://libx.org/)

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Viewing Faculty-Development Programs through the Lens of the Technological Pedagogical Content Knowledge (TPCK) Framework: Part II

In my last blog post, I promised to share more findings on viewing faculty-development programs through the lens of TPCK after trying to implement the TPCK framework into our faculty development program—DePaul Online Teaching Series, or DOTS. This program, offered in both a quarter-long and an intensive three-week format, is intended to prepare faculty to design online and hybrid courses. A total of twenty-one DePaul faculty members from psychology, public services, and education attended DOTS in spring and summer 2008.

My attempt to apply TPCK to DOTS yielded interesting results. While the overall high rating of the program showed how meaningful it is to blend technology (T), pedagogy (P), and content knowledge (CK) together through concrete examples, some feedback from faculty attested the old adage, “rules are made to be broken”—including the rules of TPCK. As I explained the rules of TPCK in my previous blog post, I ‘d like to share with you some lessons learned on how to strategically “break” the T, P, and CK bundle (as long as they can be molded back together at a certain point of the process).

Specially, here are three lessons learned from DOTS:

  • Clear the T (technology) barriers before plugging in T, P, and CK as a whole.
  • Maintain a good balance of Pedagogical preface and TPCK examples.
  • Breaking the discipline (CK) boundary with an elegant match of Technology and Pedagogy is possible.

Clear the T (technology) barriers before plugging in T, P, and CK as a whole.

If you have read Joann Golas’s post on Maslow’s Hierarchy of Faculty Support, you don’t need any more explanation about why we should clear the T barriers before doing anything else. As Joann cited in her post, Eric Larson illustrated in his presentation that faculty use of technology for teaching loosely follows Maslow’s hierarchy of needs; that is, until the basic needs—Biological and Physical, Safety, and Belongingness and Love—are taken care of, faculty will not be able to reach any higher stage on the hierarchy, including Esteem, Cognitive, Aesthetic, Self-actualization, and Transcendence.

In arranging the summer DOTS program, we made plans to take care of those “lower needs” at the very beginning:

  • The first stage, the Biological and Physical need, was addressed by providing each participant with a pre-imaged and fully tested laptop.
  • The second stage, Safety, was addressed by using technology brush-up and intro sessions to erase the fear of using technology. Two intensive tech training days were scheduled to refresh faculty’s Blackboard skills and to introduce a number of basic technology tools that faculty need to be acquainted with to become online instructors.
  • The third need, Belongingness and Love, was met by surrounding faculty with technical supporters in the training room. During the training sessions, a 1:2 staff to faculty ratio ensured that no one was left alone to struggle by him- or herself. Also, sitting with their peers in a group gave faculty the opportunity to share the same fears and desires.

This arrangement also reflects Punya Mishra’s premise of creativity, which states that the path of technology usage goes from mechanical to meaningful to generative. The mechanical stage is necessary to bring faculty on board on any type of new technology.

Faculty responses also reinforced the effectiveness of addressing their needs in a hierarchical way: the tech sessions of DOTS received almost all full scores from the participants in regard to their appropriateness on the evaluation sheets.

Maintain a good balance of pedagogical talk and examples of TPCK.

The TPCK framework carries a strong message of delivering both pedagogical and technical training through showcases—that is, to plant the T and P into the disciplinary (or the CK) context. Showcases are, therefore, a key method used by DOTS, for which many of the teaching strategies and technologies are presented in a show-and-tell mode. One thing I found by observing showcase presenters is that they usually put the “tell” (explaining the contextual/theoretical background, design philosophy and rationale, and even some lecture review) before the “show” (going through the course site). In the evaluation, faculty strongly recommended that we cut down the “front end” as to allow more time to explore the course. It is interesting to find that although almost all of the front-end talks have focused on pedagogical aspects of the design, audience still treat them as teasers before the “real thing,” and they want a teaser to be no longer than a commercial.

Will it work better to reverse the sequence from a tell-and-show mode to literally, a show-and-tell? Or what about inserting the pedagogical explanation into the “course tour” so that the “tell” is part of the “show”? The answers will be found through future DOTS sessions.

Breaking the discipline (CK) boundary with an elegant match of Technology and Pedagogy is possible!

In selecting guest speakers for the DOTS program, I wanted faculty presenters from the same discipline as the participants. I thought the ideal presenter would be someone who not only has outstanding online-teaching experiences but also speaks the same disciplinary language as our faculty participants. I believed that the relevance of content knowledge (CK) would make pedagogy (P) and technology (T) more approachable to faculty.

Yet, despite my suggestion, my staff picked, from a number of potential speakers, a person who was not in the field of psychology, education, or public services. Michelle Pacansky-Brock, an art-history professor from Sierra College was chosen to showcase her online courses. As it turned out, her session was scored the highest of all four guest speakers for DOTS. Michelle, a 2007 Sloan-C winner of the Excellent Online Teaching Award, conducted a breathtaking presentation, “Extreme Makeover: Online Course Edition,” and captured our hearts with not only her use of technology but also her passionate and devoted style of teaching. I am so glad that I wasn’t listened to, because otherwise, I would have missed Michelle, who taught me a great lesson—an elegant match of technology and pedagogy is like music that can strike beyond the linguistic boundary of any discipline.

You may click here to read Michelle blog about her experience with DOTS.

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When Details Matter

As a graduate student from the writing program working at IDD, I often wonder how much time it makes sense to devote to copy editing the online-course syllabi and modules that come across my desk. I sometimes think I’m being too stringent in my attempts to apply the rules of the Chicago Manual of Style. I have a tendency to get lost for upwards of half an hour at a time trying to resolve ambiguities of correct hyphen and comma use. (I’m still not sure if I should use a comma before a coordinating conjunction connecting two imperative clauses.)

Generally, the amount of attention that gets paid to a certain text’s punctuation, grammar, and accuracy is proportional to the number of people we expect to read it. An article in a national news magazine is rigorously scrutinized while an e-mail to officemates may not be reread once. Given that logic, it doesn’t seem to make sense to go over every course module with a fine-toothed comb.

However, I think everyone involved in producing a class should have a healthy amount of fear of students misunderstanding the course content. I bring this up because I think there’s a sense that proper grammar and punctuation, while important in order to appear professional, are purely cosmetic—at best only necessary to make a text easier to read. But something as simple as a hyphen or a capital letter can make a sentence mean something entirely different than what is intended.

In neither speech nor writing is meaning in the words alone. For example, in speech, we can distinguish the White House, the building where the president lives, from a generic house that happens to be white, by using stressed and unstressed syllables. “The white house” is not the same “the white house.” Say it out loud; you’ll hear the difference.

While we use and interpret stressed syllables naturally in speech, in writing, we have to rely on visual elements to make sure our audience reads the sentence the way it is intended. When these are absent or inconsistent, the writer loses control of what the reader interprets.

If, for example, someone referred to the syllabus for an online course as “the online course syllabus,” there’s a very real chance that the reader could interpret it instead as a course syllabus that is online, possibly assuming we are talking about a face-to-face course in which the professor posted the syllabus on Blackboard.

To prevent this kind of miscommunication, the phrase must be hyphenated as “online-course syllabus” because the words “online course” function as a compound adjective to modify “syllabus.”

Perhaps I am trying too hard to justify my existence as a writing student working at IDD. But since instructors are often trying to differentiate subtle shades of meaning and convey complicated ideas, I think every effort should be made to eliminate the potential for this kind of misinterpretation. Remember that in asynchronous learning it’s harder for students to ask and get answers to questions when they’re confused.

Of course, much of the time, students will be able to tell what you mean by context, but not always. And I think we should be on the lookout for the situations where a comma, a hyphen, or a capital letter can keep students from misunderstanding the class concepts.

Online Tools to Aid Design of Your Course

Here are a few templates and tools that can be used by a faculty member who either does not have the resources of an instructional designer at hand or merely chooses not to work with an instructional designer. The core standard for a well-designed course is the alignment of the objectives with the course assessments, learning activities and learning materials.

The central pieces of course are the learning objectives. That is where course design begins and against which course outcomes are measured.

This location is interactive and can actually help you build measurable learning objectives for your course based on Bloom’s Taxonomy! www.radiojames.com/ObjectivesBuilder

Mager’s Tips on Learning Objectives. This site includes my favorite “cheat sheet” for writing objectives: the list of observable verbs! There are two lists: one for the cognitive domain and one for the affective domain:
www2.gsu.edu/~mstmbs/CrsTools/Magerobj.html

Once the Learning Objectives are clearly written and measurable, it is amazing how the remaining course design elements will fall into place. In our training sessions designed to prepare faculty members to teach online, we’ve used several templates as guides for faculty to aid in aligning assessments and activities with objectives. Our current version is available here. As a synthesis of many other templates from across the U.S., it may very well look familiar!

Service and Online Learning

When I attended the EDUCAUSE Learning Initiative’s annual meeting in January of 2008, I was sitting in a general session, and I was thinking to myself about online education and what students ‘do’ in that environment. I then got to thinking about service-learning and how authentic, situational, and service-based assignments can be of great value to students.

All of that led to the thought that, for the most part, online learning and service-learning seem to be mutually exclusive. The question is, do they have to be?

To see what has been done in this arena, I did a search and found an article, a case study, from the EDMEDIA conference in 2002. Lesa Lorenzen Huber from Indiana University, in her paper titled “The Human Touch: Incorporating Service-Learning into an Online Course,” discusses an instance where she took on the challenge of incorporating service-learning into her online course. This was filled with a great number of challenges but also had a lot of rewards.

Service Learning Diagram

Let’s take a step back and establish the essence of service learning. According to Learn and Serve America’s National Service-Learning Clearinghouse, “service-learning is a teaching and learning strategy that integrates meaningful community service with instruction and reflection to enrich the learning experience, teach civic responsibility, and strengthen communities.” In the case of Huber’s experience, the service-learning component was to have the students serve the community by working with new, elderly residents in the area and to welcome them to the community.

Huber also had four features she wanted to be sure were included in her course, as they are important elements of any service-learning course:

  1. Service is clearly connected to the academic component and treated as a text via readings, discussion, speakers, etc.
  2. A reciprocal relationship between the university and the community makes each a partner in the education of students.
  3. Service meets a genuine community need as defined by the community-based organization.
  4. 4. The philanthropic and civic content of the students’ service is discussed and examined. It is the practice of citizenship, broadly defined, that distinguishes service-learning from practica or internships, which focus more on professional preparation.

These elements can directly lead to a rewarding student experience. However, in an online course, it becomes difficult to incorporate the element of service. How are such service projects set up with so many different communities interfacing at once? How are the variables controlled in order for service to be a ‘learning text’ when students come from different areas? How do you build a reciprocal relationship between the university and many communities?

Despite these concerns, Huber proceeded with her course. It wasn’t easy. “At the beginning of the fall semester I had decided this type of model to increase student involvement in a human services online course was just too problematic.”[i] Through the term, though, she received such overwhelming positive feedback from the students that she reconsidered.

In online courses, students often report feeling isolated while taking the class. Service-learning is one way to fix that problem. While they may not physically see their classmates, they will get out in the community and put into practice skills they are learning in the course and can then come back to the online class and discuss their individual experiences. This leads to a rich community interaction as well as a rich online discussion and interactions between students.

Expectations of online courses also become a factor. By and large, most online courses require a student only to log in to the computer and participate online or read a textbook in addition to writing papers. Online learning does not have to equate to computer-only learning. Courses can require the students to go out and complete a project, interview people, or do other types of assignments involving time and work away from the computer. Service-learning takes this to the next level, as the work outside the class and away from the Internet is not only an assignment but also a form of the text and an integral part of the course.

Service-learning courses are not easy to construct; nor are effective online courses. To combine the two together makes the creation of such a course even more challenging; however, with the greater obstacles come greater rewards and, in the end, more comprehensive and significant student learning. It is because of this that faculty should consider incorporating service-learning into their online courses and that the two do not need to be mutually exclusive.

 

[i] Huber, L. (2002). The Human Touch: Incorporating Service-Learning into an Online Course. In P. Barker & S. Rebelsky (Eds.), Proceedings of World Conference on Educational Multimedia, Hypermedia and Telecommunications 2002 (pp. 1164-1169). Chesapeake, VA: AACE.

Listening to the User

I’ve been thinking a lot about usability these days. It’s not like I never considered the user; we document and provide print and video tutorials for a host of processes and procedures here at DePaul. But I recently had a long discussion with an instructor who took me to task for assuming that students would know how to play a file in iTunes U. He didn’t know to locate and click the play icon, or to double-click the file. He was frustrated and questioned the logic of having to explain to his students the process to access a video tutorial meant to explain yet another process. My impulse was to dismiss him as a clueless Luddite, but thankfully I heard him out.

This morning I was copied on an email from an irate student who couldn’t get her course-required third-party web app to install or work properly. It didn’t occur or matter to her that DePaul didn’t design or administer the application. Since the app was a required part of her course, for her it is DePaul, and her experience struggling with the software colors her perception of her course, her instructor, and the school.

What these two incidents have in common of course is usability, or lack thereof. Both illustrate that seemingly easy tasks are often anything but easy for many users, and that these struggles have a negative impact on user satisfaction and the perceived value of a tool, course, or institution. Why do we make these usability errors?

If I’m honest with myself, I have to admit that at least regarding computer literacy I assume others know what I know simply because I know it. That it’s obvious to double-click a file to open it, or execute it, or get it to reveal its function in some way. I assume others recognize that icons exist in an application to indicate functionality or some other important attribute that the user needs to know. I assume others know to check system requirements before downloading software, or at least know what system they use. After all, I argue, it’s 2008! These things are conventions, for crying out loud! And who doesn’t know how to install an application? Do we have to explain everything?

Well, no. But we do need to explain a lot more than we might think, and we need to make things a lot more obvious. How can we do that? We might start by incorporating some quick and easy usability testing before we roll out that nifty new Web 2.0 app or learning tool in our courses. Steve Krug suggests in Don’t Make Me Think that a morning testing session with a handful of users, followed by an afternoon debriefing, is an inexpensive and effective way to find out at the beginning of a project if you’re on the right track.

What happens too often is that decisions about tools and media are made in the optimistic afterglow of a distance education conference or by instructional designers like me reacting to industry hype or instructor pressures, and then passed down as blessings from the heights of Mt. Pedagogy. Then we are surprised and irritated when users reject our offerings for being too hard to use or protest our suggestions (diplomatically worded of course) that the problem is their own technological incompetence.

Don’t get me wrong. I still believe in rich media, in interactive tools and all sorts of whiz-bang features for online courses. I’m not advocating a return to the bad old days of scrolling through endless expanses of text. But I do think it’s time to work more closely with our users, to ask them what their needs are and how we might meet those, rather than deciding for them a priori and dictating what the solutions are going to be.

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Does Anyone Like Hand-Me-Down Course Materials?

For many institutions, online course development follows a publishing model. Faculty members are recruited and compensated to “author” content that will be used by multiple instructors. This approach has several advantages:

  1. Greater Accountability: Expectations can be clearly spelled out (and enforced) through a course-development contract.
  2. Higher Quality: Course materials are often edited by an instructional designer and reviewed by other instructors.
  3. Greater Efficiency: Ideally, faculty don’t have to reinvent the wheel every time they teach a new course. The initial effort of the course author and instructional designer to create a core set of course materials saves future instructors a great deal of time in the long run.

There are also disadvantages to the publishing model. Perhaps the most commonly cited problem is the cost to the institution. Faculty who develop online courses are usually compensated with course releases and/or one-time payments comparable to what the instructor would receive to teach a single course. In addition, having course materials thoroughly edited by an instructional designer and reviewed by a panel of subject-matter experts can easily add several thousand dollars to the development costs of each course. Add usability/accessibility optimization, visual design improvements, and multimedia enhancement to the process, and the total cost per course can easily exceed $10,000.

Ten-thousand dollars can be a particularly hard number to swallow when compared to the cost of developing face-to-face courses. After all, faculty have been developing traditional courses without additional compensation for a very long time (and in K-12, the added costs of enhancing a course often come out of the instructor’s pocket). Of course, there are many arguments as to why online course development merits a considerable initial investment, such as:

  • Faculty are paid to be subject-matter experts, not technology experts.
  • The quality of the materials will be better as a result.
  • Online learning brings in tuition dollars that the institution wouldn’t otherwise receive.
  • The cost per course decreases every time the same materials are reused.

The problem that none of these arguments addresses is that many instructors (at least in my experience) simply don’t want to be required to use hand-me-down course materials. For as long as teachers have existed, many of them have shared syllabi, lecture notes, exams, and assignment concepts with their colleagues. I think most instructors value this tradition, but only when the materials are provided with no obligation.

As an instructional designer and a part-time instructor, I feel torn between two worlds. On the one hand, I recognize the benefits of clear, specific course objectives. I also see the value in providing standardized supporting materials to ensure students can meet those objectives. Yet, I also know that one of the best aspects of teaching as a profession is that you get to be the captain of your own ship (however humble it may be). You have a great deal of autonomy and, ideally, you’re free to experiment with teaching and assessment methods that might be a bit unusual as long as students master the critical course concepts.

I appreciate it when my colleagues offer to share their course materials with me, and I love to hear about what they’ve learned from their own experiences. At the same time, we have very different opinions about how to teach a course on basic web design. Some require students to write all their HTML by hand in Notepad and some introduce FrontPage on day one. I offer my students a compromise: we spend the first few weeks hand-coding before we switch to Dreamweaver.

None of our approaches have been criticized, which is fine by me since I’d sooner give myself an appendectomy with a spork than get reacquainted with FrontPage. However, that’s not to say I’m a curriculum-development anarchist. I do wish at times that my fellow interactive-design professors and I could all agree on a few things, like not introducing advanced tools like Flash or languages like JavaScript in a course where many students struggle with basic file-management concepts. Of course, I’m afraid to push for standardization because I, like many teachers, enjoy doing things my way, and I don’t want to find myself forced to teach from a pile of second-hand course materials. In the end, I like to think there’s a happy medium that embraces the best parts of the publishing model of course development while giving faculty the freedom they crave. Until then, you’ll find me slaving away over a hot laptop, creating course materials from scratch and complaining about the workload all the while.

MP3s and the Degradation of Listening

Don’t get me wrong! I own three iPods, which I use extensively and absolutely adore for their portability and other obvious advantages. I, of course, use them differently than most listeners. (If you are lazy or impatient, feel free to jump to the bottom of the page and read how.) Most listeners use mp3 players and mp3 files in ways that severely degrade sound quality and eventually deteriorate the listener’s ability to even tell the difference between good and bad sound quality. But more on this a little later.

Disclaimer: For the cynics amongst you, I am not sponsored by any record label trying to boost CD sales; I could actually not care less. All the information below is not product-specific, is based on facts, and is common knowledge to anyone with a basic understanding of the physics of sound, digital sound processing, hearing physiology, and auditory perception. Ignore at your own risk!

CD sound quality

First, let me address some fundamental issues related to the relationship between CD sound data rates and sound quality.

CD quality is usually described in terms of:

  • sampling rate (44,100 samples/sec.),
  • bit rate (16 bits), and
  • stereo presentation.

Doing some simple math, we can figure of that CD-quality sound corresponds to a data rate of 1411 kbits/sec. (44,100 * 16 * 2 = 1,411,200 bits/sec. = ~1411 kbits/sec.) Sampling rate determines the upper frequency limit (corresponding, in general, to timbre, or sound quality) that can be faithfully represented in a digital sound file (about half of the sampling rate). Bit rate determines the dynamic range (i.e. difference between the softest and strongest sound) that can be faithfully represented in a digital sound file (~6 dB per bit).

Given the maximum frequency and dynamic range of safe and functional human hearing (~20 kHz and ~100 dB respectively), CD-quality digital sound is very close to the best sound quality we can ever hear. There have been several valid arguments put forward, advocating the need for sampling rates higher than 44,100 samples/sec. (e.g. 98,200 samples/sec.), bit rates higher than 16 bits (e.g. 24 or 32 bits), and more than two channels (e.g. various versions of surround sound). Depending on the type of sound in question (e.g. the sound’s frequency/dynamic range and spatial spread) and what you want to do with it (e.g. process/analyze it in some way or just listen to it), such increases may or may not result in a perceptible increase in sound quality. So for the vast majority of listening contexts, CD-quality sound (i.e. 1411 kbits/sec. data rate) does correspond to the best quality sound one can hear.

Compressed sound quality

Now, let’s move to compressed quality sound, whether in mp3, iPod, Real, or any other format.

Every sound-compression technique has two objectives:

a) to reduce a sound file’s data rate and therefore overall file size (for easier download and storage) and

b) to accomplish (a) without noticeably degrading the perceived quality of the sound.

Sound-compression algorithms basically remove bits from a digital sound file and select the bits to be removed so that the information that will be lost will not be perceived by listeners as a noticeable loss in quality.

Compression algorithms base their selective removal of information from a digital file on three perceptual principles:

  1. Just noticeable difference in frequency and intensity:
    Our ears’ ability to perceive frequency and intensity differences as pitch and loudness differences respectively is not as fine grained as the frequency and intensity resolution supported by CD-quality sound. So it is possible to selectively remove some relevant information without the listeners noticing their removal.
  2. Masking:
    Strong sounds at one frequency can mask soft sounds at nearby frequencies, making them inaudible. It is, therefore possible to remove digital information representing soft frequencies that are closely surrounded by much stronger frequencies, without the listeners noticing the removal, since they would not have been able to hear such soft sounds in the first place.
  3. Dependence of loudness on frequency:
    Even if different frequencies have the same intensity they do not sound equally loud. In general, for a given intensity, middle frequencies sound louder than high frequencies, which sound louder than low frequencies. Given the phenomenon of masking described above, this dependence of loudness on frequency allows us to remove some soft frequencies even if they are further away from a given strong frequency, providing an additional opportunity to remove bits (information) from a digital file without listeners noticing the loss. In addition, the dynamic range of hearing is much lower for low than for middle and high frequencies and may be adequately represented by ~10 versus 16 bits, offering one more possibility for unnoticeable data-rate reduction.

Different compression algorithms (e.g. mp3, iTunes, etc.) implement the above principles in different ways, and each company claims to have the best algorithm, achieving the most reduction in file size with the least noticeable reduction in sound quality.

Digital music downloads and the stupefaction of a generation of listeners

Regardless of which company and algorithm is the best, one thing is certain. No matter how the previously discussed principles are implemented and no matter how inventive each company’s programmers are, there is no way for the above principles to support the over 90 percent reduction of information required to go from a CD-quality file to a standard mp3. In other words, reducing data rates from CD quality (1411 kbits/sec.) to the standard downloadable-music-file quality (128 kbits/sec.) is impossible without a noticeable deterioration in sound quality.

In fact, the 139th meeting of the Acoustical Society of America devoted an entire session on the matter, with multiple acousticians and music researchers presenting their perceptual studies on the relationship between compression-data rates and sound quality. Based on these and other, more recent, relevant works, it appears that data rates below ~320 kbits/sec. result in clearly noticeable deterioration of perceived sound quality for all sound files with more than minimal frequency, dynamic, and spatial spread ranges. (E.g. listening to early Ramones at low or high data rates will not make as much of a difference as listening to, say, the Beatles’ “Sergeant Pepper” album.) Such low data rates cannot faithfully represent wide ranges of perceivable frequency, intensity, and spatial-separation changes, resulting in ‘mp3s’ that include only a small proportion of the sonic variations included in the originally recorded file.

As data rates drop, there is a gradual deterioration in

a) frequency resolution (loss of high frequencies, translated as loss of clarity),

b) dynamic range (small, dynamic changes become noninterpretable by the compressed file, resulting in flatter ‘volume’ song profiles), and

c) spatial spread (loss of cross-channel differences, resulting in either exaggeration or loss of stereo separation).

When this degradation of sound quality is combined with the fact that most young listeners get their music only online, what we end up with is a generation of listeners that is exposed to, and therefore ‘trained’ in, an impoverished listening environment. Prolonged and consistent exposure to impoverished listening environments is a recipe for cognitive deterioration in listening ability. That is, in the ability to focus attention on and be able to tell the difference between fine (and, if we continue this way, even coarse) sound variations.

Such deterioration will not only affect how we listen to music but also sound perception and communication in general, since our ability to tell the difference between sound sources (i.e. who said what) and sound source locations (i.e. where did the sound come from) is intricately linked to our ability to focus attention on fine sound-quality differences.

What you should do

a) Do not listen to music exclusively in mp3 (or any other compressed) format.
Go to a live concert! Listen to a CD over a good home sound system, set of headphones, or car stereo!

b) Unless a piece of music is not available in another format, do not waste your money on iTunes or any other music download service, until such services start offering data rates greater than 300 kbits/sec.

c) When you load CDs on your iPod or other devise, select the uncompressed conversion rate (e.g. .wav or .aif formats). If you don’t have the hard disk space on your player to do this, convert at the highest available data rate (currently 320kBits/sec on iTunes).

d) Finally, get a good pair of headphones for your mp3 player! The headsets given out with iPods and most mp3 players are of such bad quality that they essentially create a tight bottleneck to the quality of your digital files and players. The response of these headphones has been designed to match the low quality of popular iTunes or other mp3 files (128 kbits/sec). Mp3-player manufacturers do this for two wise (for them) reasons:

i) poor quality headsets are cheap to produce and good enough to reproduce the poor quality mp3s files you are fed, and

ii) poor quality headsets prevent you from creating/requesting music files at higher data rates because when listening over such headphones you cannot even tell the difference between good and bad sound quality.

Well, what can I say? Wake up and listen to the music!