Re: Audio Compression


"Udhay" <udhyakumarm@xxxxxxxxx> wrote in message
news:1174883039.401672.90880@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Sir,

I am udhay. I am a student and i am working on Audio compression for
my exam.

I want to know how does the compression take place in audio??


usually, it is converted to some form that compresses better, quantized, and
run through an entropy coder.


I have doubt in human earing capacity.

it is much more sensitive than one might expect...


The maximun hearing capacity of a human is 20-20khz.


depends, I have sometimes used 20Hz sounds to tweak the results in an
autonormalizer, in part because it can be theoretically loud but inaudible,
so I insert a few loud cycles and make things a little quieter...


if a take a sample wave file,its coming around 40khz.


yes, humans hear about through this range, but this veraies from person to
person (one may have a range of, say, only about 40Hz to 12kHz, and another
may have a lot more).

the reason 44100 is typically used is because of some bizarre effect:
to generate a sound at a given frequency, you need about 2x the sample rate
as that frequency (more is better).

so, a 22kHz sound at 44kHz looks about like:

--| |--| |--
| | | |
| | | |
|__| |__|

and 11kHz looks like:

--\ /--
\ /
\ /
\__/


note that a lot of the detail in what is heard is spread over a wide
frequency range (endless overlapping waveforms), so one tries to preserve
all they can over at least the audible range.


what it mean? can anyone help me to clear this doubt..

udhay



.

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