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Next: Typical Audio Formats Up: Basics of Digital Audio Previous: Nyquist's Sampling Theorem

Implications of Sample Rate and Bit Size

Affects Quality of Audio

Signal to Noise Ratio (SNR)

Affects Size of Data




\begin{figure*}
\begin{tabular}
{\vert c\vert c\vert c\vert c\vert}
\hline
{\em ...
 ...

{\bf \footnotesize Memory Required for 1 Minute of Digital Audio}\end{figure*}

There is therfore is a trade off between Audio Quality vs. Data Rate

Some typical applications of sample bit size and sample rate are listed below:


Quality    Sample Rate  Bits per   Mono/        Data Rate        Frequency
	      (KHz)      Sample    Stereo     (Uncompressed)       Band
---------  -----------	--------  --------   -----------------  ------------

Telephone     8            8        Mono       8   KBytes/sec   200-3,400 Hz

AM Radio     11.025        8        Mono      11.0 KBytes/sec

FM Radio     22.050       16       Stereo     88.2 KBytes/sec

CD           44.1         16       Stereo    176.4 KBytes/sec   20-20,000 Hz

DAT          48           16       Stereo    192.0 KBytes/sec   20-20,000 Hz

AUDIO DEMO: Comparison of Sample Rate and Bit Size

Click on the file links below to audibly hear the difference in the sampling rates/bit sizes indicated for each file type:

File Type File Size (all mono)
44Hz 16 bit 3.5 Mb
44KHz 8-bit 1.3 Mb
22 KHz 16-bit 740 Kb
22KHz 8-Bit 424 Kb
11KHz 8-bit 120 K

Practical Implications of Nyquist Sampling Theory



We'll finish off with a question: Why are CD Sample Rates 44.1 KHz?

The answer should be obvious if you have paid attention to the above notes (Answer in Lecture).


next up previous
Next: Typical Audio Formats Up: Basics of Digital Audio Previous: Nyquist's Sampling Theorem
Dave Marshall
10/4/2001