Thread Subject: Re: 1194.25 (f) Voice Output in Public Area

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From: Gregg Vanderheiden
Date: Wed, Jun 06 2007 5:10 PM

Diane's absolutely correct.

dB is a measure of gain. Like 4 times. You can't say the volume
should be 4 times with out saying 4 times what.

dB SPL is the proper term to use for output level.

On phones we use dB alone because you are talking about gain over the input
signal. But for any product that generates its audio output we need to use
dB SPL (or dB(A) SPL)

See http://trace.wisc.edu/docs/2004-About-dB/


Gregg
-- ------------------------------
Gregg C Vanderheiden Ph.D.



> -----Original Message-----
> From: = EMAIL ADDRESS REMOVED =
> [mailto: = EMAIL ADDRESS REMOVED = ] On Behalf Of
> Diane Golden
> Sent: Wednesday, June 06, 2007 5:56 PM
> To: 'TEITAC self contained/closed products subcommittee'
> Subject: Re: [teitac-closed] 1194.25 (f) Voice Output in Public Area
>
> Couple of problems with this output requirement --
> The dB level does not specify a scale like sound pressure
> level (SPL). Assuming it means dB SPL then 65 dB SLP is
> really not sufficiently for delivery via speaker in a public
> area with any degree of ambient noise. If the audio is being
> delivered via headset, handset, or some other coupling to a
> persons ear or hearing aid - the 65 dB SPL level makes more sense.
>
> Diane Golden
> NASCIO
>
> -----Original Message-----
> From: = EMAIL ADDRESS REMOVED =
> [mailto: = EMAIL ADDRESS REMOVED = ]On Behalf Of Sean Hayes
> Sent: Wednesday, June 06, 2007 5:35 PM
> To: TEITAC self contained/closed products subcommittee
> Subject: Re: [teitac-closed] 1194.25 (f) Voice Output in Public Area
>
>
> Can you clarify whether this is intended for products
> permanently installed in a public area, or whether it is
> intended to apply to closed products like a personal music
> device or phone being operated in public area.
>
> Thanks,
>
> Sean Hayes
> Standards and Policy Team
> Corporate Accessibility Group
> Microsoft
> Phone:
> mob +44 7977 455002
> office +44 117 9719730
>
>
> -----Original Message-----
> From: = EMAIL ADDRESS REMOVED =
> [mailto: = EMAIL ADDRESS REMOVED = ] On Behalf Of
> Debbie Cook
> Sent: 06 June 2007 22:28
> To: = EMAIL ADDRESS REMOVED =
> Subject: [teitac-closed] 1194.25 (f) Voice Output in Public Area
>
> Current Language:
> When products deliver voice output in a public area,
> incremental volume control shall be provided with output
> amplification up to a level of at least 65 dB. Where the
> ambient noise level of the environment is above 45 dB, a
> volume gain of at least 20 dB above the ambient level shall
> be user selectable.
> A function shall be provided to automatically reset the
> volume to the default level after every use.
>
> Discussion:
> The only issue raised is that it is generally difficult to
> determine ambient noise level in a public place especially
> where that noise level may change.
> Can we just prescribe the 65DB and that it is otherwise user
> selectable without trying to deal with variations in ambient noise?
>
> Debbie Cook
> WA Assistive Technology Program
> Box 357920
> Seattle, WA 98195-7920
> Phone: 206-685-4181
>
>

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