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Is 24-bit Recording Really Better?
Everyone knows that 24-bit recording is better than 16, right? Even though a 24-bit recording will be reduced to 16 bits for distribution on CDs, conventional wisdom says that recording at 24 bits is always better. Especially if you apply dither during conversion to 16 bits instead of just discarding the lower 8 bits by truncating them. But is recording at 24 bits really worth the added overhead of half again more disk space and CPU power? Can anyone really hear a difference? More important, can you hear any difference?
To test this for myself - and for you too - I recorded a short section of acoustic guitar in my relatively live studio. I placed a pair of audiotechnica AT4033 microphones about four feet apart, four feet high, and three feet in front of my Yamaha FG-441S guitar having new medium gauge strings. No EQ or any other processing was used. The microphones were connected from the direct outs of a Mackie 1202 into a Delta 66 sound card, and then recorded into SAWPro using 24 bits at 44.1 KHz. I set the record levels carefully to get as close to zero as possible without overloading, and then made two copies of the original 24-bit file for these tests. One copy was reduced to 16 bits using SAWPro's "Dither Type 2" algorithm, and the other copy was simply truncated to 16 bits, also in SAW.
I then made three more copies of the truncated file in which I reduced the bit depth even further using SoundForge, to see how much deterioration could be applied before the lack of bit depth became obvious. On one copy I reduced the volume by 20 dB and then raised it by the same amount to restore the original level. The second copy was reduced and then raised by 30 dB, and the last copy was reduced and raised by 40 dB. Since 6 dB represents one bit, lowering and then raising the volume by 20 dB reduced the effective resolution to only 13 bits. For the file that was altered by 30 dB only 11 bits are now used, and the file that was changed by 40 dB uses only 9 active bits!
Your challenge is to download the five Wave files linked below, and see if you can identify which file has what resolution. But you have to tell which is which by listening to them. No fair looking at the bits in an editor program! Each of the Wave files below are just over 2.2 MB in size. Again, one file was dithered from 24 bits to 16, another was truncated, and three others were reduced to (approximately) 13 bits, 11 bits, and 9 bits respectively.
After you've made your best guesses, send them to me (click the email link on the Home page) and I'll tell you which file is which. I promise not to reveal the names of any participants, though I will tabulate the number of correct and incorrect answers and post the results publicly.
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