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Re: [Nature Recordists] Re: Olympus LS-14 initial thoughts

To: "" <>
Subject: Re: [Nature Recordists] Re: Olympus LS-14 initial thoughts
From: Max Catterwell <>
  
Well, you took on the challenge and succeeded perfectly Eric! What an excellent 
piece of analytic dissemination of, as I suspected, a complex subject. I very 
much appreciate the time you've taken to answer this question. I'm now going 
back to study this in more detail.
Cheers
Max

Sent from my iPod

On 6 Jan 2013, at 02:23, Eric Benjamin > wrote:

>> why should a preamp be called on to amplify frequencies above 20 K if nobody 
>> can hear it?
> That is an excellent question!
> 
> First we must distinguish between recordings made for analysis and recordings 
> made to be listened to by people.  If your purpose is to assess the frequency 
> range of Bat vocalizations then you had better have equipment that can record 
> it.  But you are not talking about that case.
> 
> There are several things to remember.  The first is that the frequency range 
> of 
>
> human hearing varies quite a bit between individuals.  As a rough 
>approximation, 
>
> people with smaller ear geometry have a frequency range that is shifted up in 
> frequency relative to the average.  The second is that the threshold of 
>hearing, 
>
> the level of the quietest sounds that can be heard, is not at all flat. 
> Finally, there is the important effect of auditory masking, which is probably 
> most significant of all.
> 
> It's worth taking a look at a typical threshold graph:
> 
> http://en.wikipedia.org/wiki/Equal-loudness_contour
> 
> This data is from an ISO standard, ISO 226:2003.  It's a bit of a moving 
> target 
>
> because different labs in different places get different results, and in any 
> case this curve is meant to represent an average result.  But an important 
>thing 
>
> to note is that the thresholds get worse (higher) at low frequencies and at 
>high 
>
> frequencies.  Compared to earlier editions of the standard the present one 
> doesn't have data for frequencies above 12.5 kHz.  This is because there is 
> too 
>
> much variation for them to come up with a representative figure.  The dotted 
> lines are an extrapolation. 
> 
> You can see this a bit better in Figure 1 of  this paper by the folks at 
> Etymotic Research:
> http://www.etymoticresearch.com/publications/erl-0096-1997.pdf
> 
> You will see that they show the threshold going pretty much straight up as 
> the 

> frequency approaches 20 kHz.  Hearing pretty much stops working at some very 
> high frequency.   The frequency at which this occurs does vary from 
> individual 

> to individual.  In "Recommended  High-Frequency  Audiometric  Threshold 
> Levels (8000-18  000  Hz) ", JASA Vol52, No. 2, The authors obtained a mean 
> threshold value of 59 dB at 18 kHz.  They didn't obtain data for higher 
> frequencies. 
> 
> At low frequencies the behavior is completely different.  The threshold keeps 
> rising as the frequency decreases but there is no clear cutoff.  So basically 
> the 20 Hz to 20 kHz frequency range is a misnomer.  If one were to define the 
> frequency range of human hearing as the range which we can hear at a level of 
>60 
>
> dB SPL then, using the data from the above sources, that range would be about 
>30 
>
> Hz to 18 kHz.
> 
> Finally, there is the effect of masking.  If the sound being recorded is 
>complex 
>
> and has lots of overtones then the louder, lower frequency sounds "mask" our 
> ability to hear the higher frequency sounds.  This is why we can't hear the 
> phone ringing while we're in the shower; the noise of the shower produces a 
> lot 
>
> of masking.
> 
> Backing away from all of this analysis for a bit, it's really easy to make 
> preamplifiers that amplify 20 kHz, or 40 kHz, or 200 kHz.  But it's very 
> difficult to make microphones that do that.  And even if a microphone is flat 
>up 
>
> to 20 kHz on the axis of the microphone, it almost certainly has a very 
> narrow 

> polar pattern at those high frequencies.  So it's quite conceivable that a 
> microphone that is "flat" to 20 kHz actually transmits very little sound from 
> a 
>
> subject that is off axis, effectively making a 10 kHz or 5 kHz microphone.
> 
> Eric Benjamin
> 
> 
> 
> ________________________________
> From: Max >
> To: 
> Sent: Sat, January 5, 2013 4:47:33 PM
> Subject: [Nature Recordists] Re: Olympus LS-14 initial thoughts
> 
> 
> This post of Greg's brings up an interesting question for a hearing impaired 
> person like myself. Even using both my hearing aids, I don't hear anything 
>above 
>
> 9K. Even people who hear well, as I understand it, rarely hear 20K. So, the 
> question is, why should a preamp be called on to amplify frequencies above 20 
> K 
>
> if nobody can hear it? I frequently see references to magnitudes above 20K; 
> I'm 
>
> guessing this is purely techno babble. I realise of course that these 
> frequencies are real, but humans can't hear them any more than they can see 
> in 

> the infra red.
> I feel sure that there's a perfectly logical, if complex reason for this, and 
> perhaps it's not easy to explain simply, but if it is I'd be interested to 
> hear 
>
> it.
> Cheers
> Max
> 
> --- In  Gregory O'Drobinak  wrote:
> 
>> "a preamp that may be called on to amplify frequencies above 20 KHz."
>> Greg O'Drobinak
> 
> 
> 
> 
> 
> 
> 
> ------------------------------------
> 
> "While a picture is worth a thousand words, a 
> sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
> 
> Yahoo! Groups Links
> 
> 
> 

 








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