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Old 2009-01-25, 02:17 PM
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direwolf-pgh direwolf-pgh is offline
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Re: Question about Audacity

i found this quick read interesting - other than a computer/soundcard, Im not sure whos offering 32bit playback
Quote:
16 Bit
16 bit matches audio CDs, and is thus suited where the better dynamic range and S/N ratio of CD quality audio is required. 16 bit is a good general purpose high quality setting. 16 bit recording is suitable for vinyl records.

24 Bit
24 bit recording may be used for signals that will be manipulated but still need to maintain the full 16 bit quality of CD audio. 24 bit is good for mastering.

If you're merely listening to thousands of pounds of expertly chosen high end audio kit, and not doing large amounts of editing, there may be no real reason to exceed 24 bit depth.

32 Bit
Some see 32 bit recording as taking things to extremes. Although 32 bit recording can in theory have better technical specs than less bits, it is not often such great bit depth is needed. General purpose recording does not need 32 bit depth for the same reason clothing sizes do not come in increments of 1/1000th of an inch.
Finding audio sources capable of providing signals with better dynamic range than than 24 bit resolution is a demanding task. A 32 bit data stream records 65,000 times the dynamic range of 16 bit CD audio. In real world applications, a lot of those bits will be normally recording nothing but very low level background noise.

Also bear in mind that in many cases you will exporting to a 16 bit format (there are not many computer media players that support playing 32 bit files, and if you are burning to a standard audio CD, that format is by definition 16 bit).

But if you want the highest standards (for example, operate a recording studio), expect to do a large amount of manipulation of the data before export, and have audio source equipment with an extremely low noise floor, 32 bit recording (which is the default setting in Audacity) will give the best possible quality and avoid the bit depth having any effect on the sound even after heavy manipulation of the audio.

Much of the reason for this is that Audacity uses "float" format for 32 bit recording instead of fixed integer format. Normalised floating point values are quicker and easier to process on computers than fixed integer values and allow greater dynamic range to be retained even after editing. This is because intermediate signals during audio processing can have very variable values. If they all get truncated to a fixed integer format, you can't boost them back up to full scale without losing resolution (i.e. without the data becoming less representative of the original than it was before). With floating point, rounding errors during intermediate processing are negligible.

The (theoretically audible) advantage of this is that 32-bit floating point format retains the original noise floor, and does not add noise. For example, with fixed integer data, applying a compressor effect to lower the peaks by 9 dB and separately amplifying back up would cost 9dB (or more than 2 bits) of signal to noise ratio (SNR). If done with floating point data, the SNR of the peaks remains as good as before (except that the quiet passages are 9dB louder and so 9dB noisier due to the noise they had in the first place).

The advantage of using 32 bit float to work with holds even if you have to export to a 16 bit format. Using Dither on the Quality tab of Audacity Preferences will improve the sound quality of the exported file so there are only minimal (probably non-audible) effects of downsampling from 32 bit to 16 bit.

Retrieved from "http://audacityteam.org/wiki/index.php?title=Bit_Depth"
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