[LINK] Hearing tests for free by phone (o/t)

[Ivan Trundle]

That's the kind of response I expect and enjoy from being on Link.

Thanks Stephen - wonderful info.


On 29/02/2008, at 4:32 PM, stephen at melbpc.org.au wrote:

> BRD writes:
>
>> Ivan Trundle wrote:
>>
>>> And why just a fixed phone? The acoustic ability of my 'fixed' phone
>>> is no better than that of my mobile - or perhaps someone who knows
>>> can tell us what frequency ranges are possible across both options
>>
>> The frequency response of POTS is about 400 Hz to 3400 Hz.
>
> I'm not sure that the NAL specifically request that people wanting  
> to do
> an initial screening-test of their hearing use a fixed-line phone,  
> rather
> than a mobile phone, because of any differing audio frequency  
> responses ..
>
> (Quote) A mobile phone's audio quality depends on its audio  
> amplifiers'
> power output and its speakers' impedance. Typically, a standard 3.6- 
> volt
> battery powers two class D amplifiers to drive a pair of 8-ohm  
> speakers.
>
> In the CAP-XX tests, this set-up delivered peak power of 1.2 watts  
> (W) to
> 2.25W. This lack of power can result in thin-sounding music with a  
> weak
> bass beat.
>
> Another problem arises when the battery becomes taxed from  
> simultaneous
> peak power demands to transmit wireless data and respond to a  
> network poll
> [networks periodically poll phones to locate them and determine needed
> transmit power] while the user is also listening to music. The battery
> voltage droops, and the audio amplifier supply voltage may droop  
> enough to
> cause distortion which the user hears as a "click." This problem is  
> worse
> in GSM/GPRS/EDGE phones which require particularly high power for  
> radio-
> frequency (RF) transmission.
>
> In addition, a 1-Amp or greater peak-power demand on the battery will
> cause a ripple in the audio amplifier supply voltage which the user  
> hears
> as audio noise, or as a 217Hz buzz during a phone call. <http://www.cap 
> -
> xx.com/news/BriteSoundPowerArchitecture.htm>
> --
>
> Cheers, people
> Stephen Loosley
> Victoria,
> Australia
>
> Message sent using MelbPC WebMail Server
>
>
>
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--
Ivan Trundle
http://itrundle.com ivan at itrundle.com
ph: +61 (0)418 244 259 fx: +61 (0)2 6286 8742
skype: callto://ivanovitchk