How to calculate audio file size?

Question

You have 30 seconds audio file sampled at a rate of 44.1 KHz and quantized using 8 bits ; calculate the bit rate and the size of mono and stereo versions of this file ؟؟

Embowed

What kind of calculation have you tried? – Decemvir

kHz = "1000 per second", bitrate = "bits per second" - the math is rather obvious. – Valida

file size mono 30 * 44.1 = 1323 K stereo 30 * 44.1 * 2 =2646k --------------------------------------- bit rate = filesize / seconds ------------------------------ but my problem with this line "and quantized using 8 bits " how it will affect the math ??? – Embowed

@OsamaAl-far "quantized using 8 bits" is fairly meaningless. Can you better describe what you are trying to do? Surely you mean that the audio is sampled at 8 bits per sample? – Kaleena

@Kaleena BUT AT THE QUESTION IT ASK TO CALCULATE THE BIT RATE , IS IT EQUAL TO 8 ?? – Embowed

@OsamaAl-far, Your bit rate is the number of bits per second. Read my answer. – Kaleena

Answer 1

The bitrate is the number of bits per second.

bitrate = bitsPerSample * samplesPerSecond * channels

So in this case for stereo the bitrate is 8 * 44100 * 2 = 705,600kbps

To get the file size, multiply the bitrate by the duration (in seconds), and divide by 8 (to get from bits to bytes):

fileSize = (bitsPerSample * samplesPerSecond * channels * duration) / 8;

So in this case 30 seconds of stereo will take up (8 * 44100 * 2 * 30) / 8 = 2,646,000 bytes

Fervid

You saved my exam! – Incautious

I'm pretty sure the units is wrong here for the bit rate calculation? Are you sure you don't mean 705,600 bits per second not 705,600 kilo bits per second...? – Dumas

Answer 2

Assuming uncompressed PCM audio...

time * sampleRate * bitsPerSample * channelCount

For 30 seconds mono audio at 44.1kHz, 8bps, that's 1,323,000 bytes. For stereo, that's two channels, so double it.

Kaleena

30 * 44.1 * 8 = 10584 . HOW DID YOU CALCULATE 1,323,000 bytes. ? – Embowed

44.1k = 44100, not 44.1, so 30*44100*8. – Karilynn

@OsamaAl-far to get from bits to bytes you must divide by 8 – Fervid

Answer 3

Formula = Sample rate x sample bit x # of channels x time in seconds / 8x1024

CD Quality (Sample Rate) = 44.1Khz

Size of mono = (44 100 x 8 x 1 x 30) / 8 x 1024
             = 1291.99KB
             = 1.26 MB


Size of Stereo = (44 100 x 8 x 2 x 30) / 8 x 1024
               = 2583.98 KB
               = 2.52 MB
               ≈ 2.5 MB 

Reparation

Don't forget that CD quality is indeed 44.1khz, but 16bits, not 8. Even if the question is asking for 8 bits, this might be a bit confusing to read. – Cupidity