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From: lanmaint@nssdcb.gsfc.nasa.gov (Dave Yoest)
Newsgroups: comp.sys.apple2
Subject: Re: What's wrong with this Pascal program?
Keywords: pascal
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Date: 24 May 91 17:02:30 GMT
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In article <5397@cernvax.cern.ch>, myb@cernvax.cern.ch (michel bornand) writes...
>Hi everybody! Here is a simple Pascal program for Apple IIGS which should
>produce a sound at 16kHz. It does not work. What's wrong with it?
>What did I miss?
> 

code deleted

>Thank you for all suggestions.
> 
>Micky



Well,

 I don't know any apple, so you code might be fine, it might not work 
 at all. But keep the following in mind.

 1. The frequency response of the human ear rolls off at roughly
    14 KHZ. This means that at high frequencies you will need
    much more volume than the frequencies under 10KHZ. At some
    point you won't be able to hear the tone at all. This varies
    from individual to individual, and some rare individuals may
    be able to hear to 20 KHZ, but 16 KHZ is in the range where
    many people will not be able to detect the tone.

 2. The speaker you are driving must be able to produce a 16KHZ
    tone. The speaker built into the monitor you are using might
    not be capable of producing a tone at this frequency.



Suggestions:

 1. Try generating a 12KHZ tone. You should be able to hear that.
    Then a 13KHZ, Then 14KHZ etc. You may be able to determine if
    you can hear a 16KHZ tone. If you've never heard a 16KHZ tone
    before, you might not have a concept of what a tone of that
    frequency sounds like. I used to work on a lot of TV equipment
    , and with practice could detect the Horizontal oscillator
    frequency (actually the resonation of mechanical parts in the
    horizontal) at 15,734 HZ. It took some time to gain this ability
    because I didn't have the concept of a 15KHZ tone at first. The 
    step-up method might help you gain this concept.

 2. Preferred.... Use an oscilliscope connected to the audio output
    and look for the electrical signal that you want to drive the 
    speaker with. This method will also allow you to verify the
    accuracy of the frequency.


 3. See if the dogs in your area respond. 8-)


Dave Yoest
LAN M&O Section Supervisor
NASA/Goddard Space Flight Center
Greenbelt, Md. 20771

DYOEST@128.183.43.16
DYOEST@zaphod.gsfc.nasa.gov