Audio Compression

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??

I have doubt in human earing capacity.The maximun hearing capacity of
a human is 20-20khz.

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

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

udhay

On Mar 26, 12:25 am, "Udhay" <udhyakum...@gmail.com> wrote:
> Sir,

some of the ladies that follow this newsgroup might be offended by the
assumption.  (but then again, i dunno specifically who they are.)

> 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??
>
> I have doubt in human earing capacity.The maximun hearing capacity of
> a human is 20-20khz.
>
> if a take a sample wave file,its coming around 40khz.
>
> what it mean? can anyone help me to clear this doubt..

particular to the field of audio signal processing, there can be at
least two different meanings to the term "compression".  usually it
means level compression and you could buy devices that do that for 5
decades or more.  the other meaning. more recent, is data
compression.  it could also mean "time compression" a.k.a. "time
scaling" for when the scaling factor is less than one, but i doubt
that is what you're inquiring about.  can you tell if it's about level
compression of audio signals or data compression of audio?

r bpj

On Mar 25, 9:35 pm, "robert bristow-johnson"
<r...@audioimagination.com> wrote:
> On Mar 26, 12:25 am, "Udhay" <udhyakum...@gmail.com> wrote:
>
> > Sir,
>
> some of the ladies that follow this newsgroup might be offended by the
> assumption.  (but then again, i dunno specifically who they are.)
>
> > 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??
>
> > I have doubt in human earing capacity.The maximun hearing capacity of
> > a human is 20-20khz.
>
> > if a take a sample wave file,its coming around 40khz.
>
> > what it mean? can anyone help me to clear this doubt..
>
> particular to the field of audio signal processing, there can be at
> least two different meanings to the term "compression".  usually it
> means level compression and you could buy devices that do that for 5
> decades or more.  the other meaning. more recent, is data
> compression.  it could also mean "time compression" a.k.a. "time
> scaling" for when the scaling factor is less than one, but i doubt
> that is what you're inquiring about.  can you tell if it's about level
> compression of audio signals or data compression of audio?
>
> r bpj

Sir

Thanks for your reply.

I want to know about the data compression of audio.

i need some links regarding this.

which algorithm is good example for audio compression?

udhay

Udhay wrote:

> Thanks for your reply.
> 
> I want to know about the data compression of audio.
> 
> i need some links regarding this.
> 
> which algorithm is good example for audio compression?

MP3 is widely used for music and general sounds. Other methods are more 
efficient for voice, especially voice telephony. See 
http://www.howstuffworks.com/mp3.htm

Jerry
-- 
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

>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??

I think you have already got the answer for this question


>I have doubt in human earing capacity.The maximun hearing capacity of
>a human is 20-20khz.
Yes, a human can hear between 20 to 20K hertz. But the response is not the
same for all frequencies. It follows some standard curves(i think it is an
inverted U or a U, not sure.)


>if a take a sample wave file,its coming around 40khz.
The sample wave file you are taking might have a sampling frequency of
44.1 Khz(which is around 40Khz), which is a standard sampling rate. I dont
know what you meant by 'its'.

>what it mean? can anyone help me to clear this doubt..
It means that the audio in the wav file has been sampled at 44.1 Khz.. 

>udhay
aps
>

Jerry Avins wrote:

>> I want to know about the data compression of audio.
>>
>> i need some links regarding this.
>>
>> which algorithm is good example for audio compression?
> 
> 
> MP3 is widely used for music and general sounds. Other methods are more 
> efficient for voice, especially voice telephony. See 
> http://www.howstuffworks.com/mp3.htm
> 

Not forgetting free/open-source alternatives: [Ogg]Vorbis for lossy 
compression and FLAC for lossless compression:

http://www.xiph.org

To discuss compression thoroughly, it is important to understand and 
document the difference between lossy and lossless forms (and between 
them and plain binary data compression a la gzip, etc). As usual, 
"Google is your friend".

Richard Dobson