4 ms·

How about percussive sounds, such as a cymbal crash? These show very high frequencies in a Fourier analysis. Wouldn't that invalidate the application of the Nyq

by isolli 8y ago

How about percussive sounds, such as a cymbal crash? These show very high frequencies in a Fourier analysis. Wouldn't that invalidate the application of the Nyquist-Shannon theorem?

louthy 8y ago
It's worth watching the video in my references [1] - it's a proper hacker's view of digital audio and how it translates to the analogue domain. Even with a 20khz sound you're not going to get any aliasing at 44khz sample rate. Most people's hearing starts to fall off significantly after around 12khz or so (depending on age). Most cymbals have a fundamental frequency around 2-5khz in my experience. Also, because cymbal sounds are pretty close to being noise, it's arguable whether it would matter or not. Although if you listen to a 128 kbps MP3 then you can often hear the top end frequency sounds (like cymbals) becoming 'mushy'. To the vast majority of people once you get to 192 kbps it's inaudible, and then above that most people with 'perfect ears' would struggle. And that's with a lossy format, never mind the lossless formats of CDs, WAV or FLAC which is the discussion at hand. [1] https://www.youtube.com/watch?v=cIQ9IXSUzuM https://www.youtube.com/watch?v=cIQ9IXSUzuM
squeaky-clean 8y ago
The ADC (Analog-digital-converter) will always have an anti-aliasing lowpass filter to remove any frequencies above the nyquist and prevent aliasing in the recording. Sometimes it's analog, nowadays it's often a 2-stage system with oversampling and a digital anti-aliasing filter. But the result that goes into the recorder is the same, any frequencies above the Nyquist (which would become aliased and mirrored) are removed or reduced to inaudible levels before being finally digitized. So while cymbals do have lots of high frequency content, in a 44.1khz recording any frequencies at or above 22.05khz should be removed first. (In reality it's not a brickwall filter at that frequency, but tends to steeply roll off once it gets nearer). Unless I'm misunderstanding what you're asking.

by isolli 8y ago

How about percussive sounds, such as a cymbal crash? These show very high frequencies in a Fourier analysis. Wouldn't that invalidate the application of the Nyquist-Shannon theorem?

louthy 8y ago

It's worth watching the video in my references [1] - it's a proper hacker's view of digital audio and how it translates to the analogue domain. Even with a 20khz sound you're not going to get any aliasing at 44khz sample rate. Most people's hearing starts to fall off significantly after around 12khz or so (depending on age). Most cymbals have a fundamental frequency around 2-5khz in my experience. Also, because cymbal sounds are pretty close to being noise, it's arguable whether it would matter or not. Although if you listen to a 128 kbps MP3 then you can often hear the top end frequency sounds (like cymbals) becoming 'mushy'. To the vast majority of people once you get to 192 kbps it's inaudible, and then above that most people with 'perfect ears' would struggle. And that's with a lossy format, never mind the lossless formats of CDs, WAV or FLAC which is the discussion at hand. [1] https://www.youtube.com/watch?v=cIQ9IXSUzuM https://www.youtube.com/watch?v=cIQ9IXSUzuM

squeaky-clean 8y ago

The ADC (Analog-digital-converter) will always have an anti-aliasing lowpass filter to remove any frequencies above the nyquist and prevent aliasing in the recording. Sometimes it's analog, nowadays it's often a 2-stage system with oversampling and a digital anti-aliasing filter. But the result that goes into the recorder is the same, any frequencies above the Nyquist (which would become aliased and mirrored) are removed or reduced to inaudible levels before being finally digitized. So while cymbals do have lots of high frequency content, in a 44.1khz recording any frequencies at or above 22.05khz should be removed first. (In reality it's not a brickwall filter at that frequency, but tends to steeply roll off once it gets nearer). Unless I'm misunderstanding what you're asking.