Thread Subject: Re: Amplification and Research
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From: Michaelis, Paul R. (Paul)
Date: Sun, Mar 25 2007 11:15 AM
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The idea that lack-of-distortion would be at least as important as
amplitude for hard-of-hearing listeners makes perfect sense to me.
A nice thing about amplitude is that it's easy to measure and quantify,
thereby making it easy to write testable engineering requirements for
Sections 255 and 508. (Although we may not agree about the decibel
level that should be required, we do agree that dB is the appropriate
unit of measure.)
Here's the problem: If you were to write an engineering requirement
oriented toward people who are hard-of-hearing, specifying a minimal
acceptable level of intelligibility and audio distortion, how would you
word it so that manufacturers and contract officers could tell whether a
product satisfies users' needs? I'm keeping my fingers crossed that
someone with training in audiology -- perhaps the person who did your
daughter's ipod test -- might be able to suggest metrics we could use.
-- Paul Michaelis
From: Jagbell [mailto: = EMAIL ADDRESS REMOVED = ]
Sent: Sunday, March 25, 2007 10:24 AM
To: TEITAC Telecommunications Subcommittee
Subject: Re: [teitac-telecom] Amplification and Research
I am reaching out to the person who performed the ipod test with my
daughter. If he is interested, can he join the group to discuss this
On Mar 25, 2007, at 11:52 AM, Michaelis, Paul R. (Paul) wrote:
> I believe that the issue of intelligibility for hard-of-hearing users
> is extremely important. I'm struggling with how to write requirements
> for Section 508 that would achieve what we want.
> A problem is that many of the techniques that are commonly used to
> assess telecom voice quality are oriented toward differentiating among
> products that, for most people, are fully intelligible. The goal is
> to measure perceived quality, rather than intelligibility. This is
> why these tests are described as "subjective" with the results
> reported as a "Mean Opinion Score." Although the conduct of such
> tests is a standard part of our product development process, I have
> absolutely no idea whether our measures of perceived quality would
> correlate highly with intelligibility among listeners who are
> Tests for intelligibility do exist. Examples of procedures that rely
> on human assessment include the Diagnostic Rhyme Test and the Modified
> Rhyme Test. Unfortunately, given the wide variation among people who
> are hard-of-hearing, it would be impractical for me to hire a
> statistically valid sample of hard-of-hearing listeners in order to do
> DRT and MRT tests for each of my products. The tests that measure the
> physical properties of the speech -- for example, the amplitude and
> signal-to-noise ratio of the speech at different parts of the acoustic
> spectrum -- work pretty well as a predictor of intelligibility for
> people with normal hearing. Are these tests valid for people who are
> A bigger problem is that the voice quality in a VoIP system can vary
> tremendously depending on factors that are outside the vendor's
> control, and beyond the ability of a typical contract officer to
> assess. For example, an IP network that has excellent voice quality
> under normal conditions may have unacceptable quality when the system
> is heavily loaded with voice traffic -- as might happen during an
> emergency or during times of the day when large numbers of conference
> calls tend to be scheduled. This is because higher levels of traffic
> can cause increased packet loss, packet jitter, and packet latency,
> along with a need to shift from uncompressed G.711 audio encoding to a
> compression technique such as G.729. I have no idea how to write an
> acceptable requirement that addresses this issue.
> Despite the complexity of these problems, I'm sure we can do a better
> job for hard-of-hearing users than simply to require support for
> increased amplification. I'm looking forward to hearing people's
> -- Paul Michaelis
> -----Original Message-----
> From: Jim Tobias [mailto: = EMAIL ADDRESS REMOVED = ]
> Sent: Sunday, March 25, 2007 7:15 AM
> To: 'TEITAC Telecommunications Subcommittee'
> Subject: Re: [teitac-telecom] Amplification and Research
> David, you are quite right to differentiate between amplification and
> clarity, of course. A louder bad signal is not a better signal.
> in rock music, of course.
> Clarity itself is made up of several different characteristics, as
> Paul has already responded. I readily admit to not being an expert in
> this area.
> But I do know that there is a set of industry measures (or at least
> testing protocols and metrics) for intelligibility that are commonly
> applied to telephones. In fact, there's a whole family of them, P.800
> from ITU, and another one from ITU, G.107. Most (all?) of these use
> subjective testing: a bunch of people listen to the audio and rate it
> on a scale of intelligibility. (Who is in that bunch, of course, is
> an interesting question -- you have to wonder if they automatically
> rule out anyone with any hearing loss!) The answer is a number. For
> the most common metric, MOS (great to have an acronym, but all it
> stands for is "mean opinion score"), a rating above 4.0 out of 5.0 is
> considered good.
> TEITAC or the Access Board could decide to research this issue to find
> 1. if any other worldwide accessibility regulations use one or more of
> these measures 2. if any US regs for any purpose use one or more of
> these measures 3. if procurement ever includes any such requirements
> which, if any, of the metrics are commonly used by vendors
> and perhaps other points about the utility and feasibility of adopting
> a metric. One interesting question would be to map the metric onto
> the world of hearing loss. For example, how many people with what
> kind and degree of hearing loss can detect a difference between a 3.5
> and a 4.5 MOS.
> Jim Tobias
> Inclusive Technologies
> +1.732.441.0831 v/tty
> +1.908.907.2387 mobile
> skype jimtobias
> -----Original Message-----
> From: Baquis David [mailto: = EMAIL ADDRESS REMOVED = ]
> Sent: Monday, March 12, 2007 4:03 PM
> To: = EMAIL ADDRESS REMOVED =
> Subject: [teitac-telecom] Amplification and Research
> I have skimmed an archived thread of discussion about amplification as
> well as listened to part of today's call. Here are my thoughts as you
> prepare to present your work-to-date to the TEITAC:
> Remember that you can recommend that the Access Board research an
> We would likely do that by funding a contractor. Your recommendations
> need not be limited to comments about the Standards/Guidelines.
> Would you like research on what is sufficient for hearing access over
> the telephone? I know, of course, that the answer to this is complex
> since there are different types of hearing loss, telephones,
> situations, etc. And yet, you are recommending design standards to
> help with such access.
> For a second, let's set aside the legal issues as well as the burden
> and begin with an understanding of what people who are hard of hearing
> really need for accessibility, if we can. In this paragraph, I am not
> addressing what problems we might encounter if we try to accomplish
> this. I am simply asking what is truly helpful.
> * When is 20 dB, 25dB, up to 40dB beneficial? Are these demands
> based solely on anectodal reports? If there is a science to this,
> shouldn't we discover it? If it is already known, could it be
> referenced as a basis for rulemaking? If we do not know this with
> research-based certainty, wouldn't you like to recommend that it be
> * How does clarity interrelate with amplification? If clarity is
> improved, does that partially reduce the need for high gain? Does the
> subcom need technical information on what specific elements make up
> * Is a separate standard for clarity needed?
> * Any other questions regarding maximizing residual hearing to add
> to this list?
> Looking back to Brenda's email from November 6, 2006, I see that HLAA
> commissioned lab research to address distortion. Would it be helpful
> to the TEITAC to know of other research, such as this, which could
> help inform rulemaking? Brenda, do you want to post that research on
> the wiki (or ask Tim to do it). If the TEITAC feels that distortion
> caused by amplification is a non-issue then perhaps that should be
> stated clearly as a point of agreement.
> Since we are looking at both 255 and 508, consider the impact not only
> on the government customer (508) but on the individual consumer (255).
> Of course there is the impact on manufacturers too, so you may want to
> lay this out in an easy to follow chart - with both positive and
> negative impacts included.
> With regard to Paul's comment on battery drain to provide
> amplification at higher levels, you may want to consider commenting on
> wireless and wireline separately if that makes a difference in
> respective impact. I am imagining not only economic impact, but
> consumer satisfaction with a phone that may not work as well.
> However, I am also imagining that the past does not equal the future.
> What feels impossible now may become possible in the future with
> improvements in batteries, processing, etc.
> Oh and don't forget VoIP and network-based amplification when you
> consider possibilities and impacts. Do you imagine old technology or
> new technology when discussing this? Must the power for the volume
> always be contained inside the phone set? How far away are we from the
> day when our preferred hearing interface can be profiled -- and we can
> virtually bring that profile with us from phone to phone (or multiple
> profiles depending on changes in environment, congested hearing, etc)?
> And what would be the hardware requirements to support a network-based
> David Baquis
> Accessibility Specialist
> U.S. Access Board
> 1331 F Street, NW, #1000
> Washington, DC 20004
> 800-USA-ABLE; (202) 272-0013 (voice)
> www.access-board.gov; = EMAIL ADDRESS REMOVED = "Leading the
> way to
> excellence in accessibility"