Sampling rate & resolution

[Shugidy]

jus a quick question ... what is this ?? is it the higher the sample rate the better quality ?? and the resolution too ... what is the difference when recording with a higher resolution then a lower one ?

[Massive Master]

The sample rate determines the highest frequency that can be reproduced (Google "Nyquist Theorum" for more). Human hearing is limited to around 20Hz to 20,000Hz. A 44.1kHz sampling rate (like a CD) will accurately reproduce 22,050Hz - Slightly higher than the basica human hearing range, and considerably higher than a lot of audio equipment.

Got that so far?

Bit depth (a.k.a. word length) is measured in bits and is a measurment of the resolution OF the sample. A 1 bit sample has only two possible values - "ON" and "OFF." When you go up, the numbers go up exponentially - On a 16 bit recording (like a CD), any one sample (there are 44,100 of them per second) can have one of around 65,000 values. That's a reasonable resolution. A 24-bit signal on the other hand will have one of 16.7 million values - A huge jump in accuracy, and basically the "standard" word length for audio recording.

So what you find the majority of the time - Rookies, Hobbyists, Semi-professionals, Recording Top Guns - is 24-bit recording *at the target sample rate* (44.1kHz for music CD production, 48kHz for video, etc.). Some prefer to record at higher sample rates, others don't. There are sensible arguments on both sides. But one thing that few (if anyone) will deny is that if you can't get 44.1kHz to sound absolutely wonderful, going up to a higher sample rate isn't really going to help.

[superspit]

Originally Posted by Shugidy

jus a quick question ... what is this ?? is it the higher the sample rate the better quality ?? and the resolution too ... what is the difference when recording with a higher resolution then a lower one ?

Sampling rate and resolution must be taken into account when recording digitally. For example, in a CD, digital sound is encoded as 44.1 kHz, 16 bit audio. This means that the original wave is 'sliced' 44,100 times a second - and an average amplitude level is applied to each sample. The variety of different amplitude values available is dependent on the resolution. 16 bit means that a total of 65,536 different values can be assigned, or quantized to each sample. Therefore, the higher the sample rate and resolution, the higher the quality of the audio, because a wave closer to that of the original audio can be stored. For comparison, DAT can store audio at up to 48 kHz, whilst DVD-Audio can be 96 or 192 kHz and up to 24 bits resolution. This affords a significant increase in sound quality.

Hope that helps?
Ofcourse, there will be those who disagree with the above, as they believe that the extra space required, on a hard drive, for example, is not proportional to the potential increase in quality of the sound being recorded. And that's fine too!!
Superspit

[dobro]

John, if CD players played 88.2, we'd all be recording and mixing and burning out stuff at that rate, right? And happier about it in terms of sound, right?

[Massive Master]

Eh, most gear out there can't handle those frequencies anyway. Microphones, preamps, compressors, amplifiers, speakers -

24-bit resolution is important to me - I wish CD's were 24-bit.

88.2kHz is important to dog whistles - If anything else in the chain could reproduce the signal in the first place.

Gee, that sounds negative - I don't mean it to. I actually have several pieces of gear that can handle those frequencies - But I still don't bother recording at high sample rates. I'll admit that some of the upsampling plugs I've used probably wouldn't have as much "magic" in them if they didn't upsample. But as far as actually capturing the sound, 44.1kHz, done well, sounds excellent.

[dobro]

Okay, fair enough. But why would you like CDs to be 24-bit?

[Massive Master]

16-bit = 65,000 possible values (resolution detail)

24-bit = 16.7 million values.

That's pretty serious resolution...

[dobro]

So - bitdepth is a more important determinant of audible resolution than sample rate...

Interesting. I would have thought it was the other way around. That's one of the many reasons why I'm not an engineer.