Voice sample is stored as 1 byte. Freq range:16Hz to 20 Hz. What is the memory size required to stored 4 mins?

Question

Its just a question asked in some Aptitude test. Can you guys please help me to find this ...

Answer 1

You really can't just sample from 16Hz to 20Hz, you would have to sample from 0-20Hz and then remove what you don't need. Anyhow, you would need to sample at 2 x the frequency of the desired range to prevent the recording from becoming distorted. So, to record a 20Hz sound, you would have to sample at 40Hz. We are going to be sampling at 8 bits (aka 1 byte). So here is how the math works. 40,000 samples/second * 8 bits/sample = 320,000 bits/second / 8 bits/byte = 40kB/second * 240 seconds = 9,600 kB. To get this number into MB you divide by 1024 for a total of 9.375MB. This is uncompressed of course.

Answer 2

Are you sure about the frequency range? The memory size will depend on your sample rate. You don't say that. To get a good intelligible voice, you can limit your frequency response between about 300 and 3 kHz.

Answer 3

At 44100 kHz, stereo - it takes 10Mb per minute for native .WAV data.

So - for 11kHz, mono - you need 1.25 Mb per minute.

What the problem is actually testing you on is your knowledge of how often you have to sample, given a frequency range, in order to "faithfully" reproduce the data, without "aliasing". In order to accurately reproduce 20Hz, you need to sample at about 200Hz (there is a name for figuring out how often you have to sample, but it escapes me at the moment...).

200 per second times 60 seconds per minute, times 4 minutes, times 1 byte = .....

....hey, I already have my degree....do your own homework....