Re: What is sound and how is it represented?
I would highly recommend Mark Heath's Digital Audio Fundamentals course on Pluralsite, available at https://www.pluralsight.com/courses/dig … damentals. In short:
* A wav file is a container; this is the same for other "container" formats like MP4 and Ogg. You can throw an MP3 file in a WAV file, or in an OGG file, or in an MP4 file.
You asked about audio frames and audio samples. An audio frame is a collection of audio samples. An audio sample is either an integer or a floating point number. This is where things get a bit complicated.
In audio formats, a very important concept is the sample rate. An audio file consists of hundreds of thousands, if not millions to billions, of samples, and the sample rate determines how many samples you will send to the sound card per second. The most common is 44,100 Hz, though there are higher sample rates too (i.e. 192,000 Hz). If your sample rate is 192,000 Hz, then you are actively blasting the sound card with 192,000 samples per second, or 192 samples per millisecond.
Now, lets cover something even more relevant to sample rates: the Nyquist Frequency. The nyquist frequency is hwo high, in Hertz, you will be able to capture in an audio recording. Its more mathematical name is 'Nyquist-Shannon Sampling Theorem'. The Nyquist-Shannon Sampling Theorem states that the maximum frequency you will be able to capture from any audio input is half the actual sample rate that you are wanting to capture your audio at. For example, if your recording at 44.1 KHz, then you will only be able to capture up to 22.05 KHz. So what happens to the rest? Its this little problem called 'aliasing'. If you sample a sine wave at 30000 Hz, you will get an aliased sine wave that is far lower than the one your trying to sample. This is a very bad thing, and to avoid that, we use a low-pass filter.
The course I've linked above has far more information on the subject; I need to go to class now, but please do listen to it and enjoy!
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