Tim Wescott wrote:> Ritual wrote:...>> What happens to the information between the single bit samples on the >> waveform? > > Information about voltages between the possible ADC output values is lost.That is the case with any measurement. Counting can be exact, but any measurement is of limited accuracy. \>> What happens to the information between the time on the X >> axis? > > That is lost also.I have to disagree. Only information above half the sample rate is lost. (There better not be any anformation above half the sample rate. It would corrupt the entire signal with aliases.) Information about the entire continuous and properly sampled signal is retained in the samples. That's fundamental to digital processing.>> Someone told me that since the human ear can only hear >> frequencies up to 20kHz that sampling rates above this are >> unnecessary, but I don't buy it even though I can't put my finger on >> it.Sampling above 40 KHz is needed to reproduce 20 KHz. Some of the system needs to be analog (anti-alias prefilter and reconstruction postfilter). The higher the sample rate, the easier these are to build. ...>> I can't get it out of my head that digital representation of an >> analog signal is going to throw away some data.Sure, but so does any other system of representation and recording. It's not possible to copy something perfectly by any means. There are always losses, distortions, and artifacts.>> A finite >> representation of an infinite source. My audio soft/hardware offers >> sampling setups up to 96kHz and 32 bits per sample. It just seems to >> me that there is no limit to which one could push these numbers and >> still not reach the original.You can reach the limits of audible frequencies at sampling rates far below 96 KHz. You can exceed the accuracy of tape or vinyl with numbers smaller that 32 bits. There are four important points of comparison for audio: frequency response, dynamic range, signal-to-noise ratio, and distortion. Digital systems can match or outdo analog in all of them. Jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

# Help understanding audio sampling

Started by ●April 14, 2007

Reply by ●April 15, 20072007-04-15

Reply by ●April 15, 20072007-04-15

Tim Wescott wrote:> Ritual wrote:...>> What happens to the information between the single bit samples on the >> waveform? > > Information about voltages between the possible ADC output values is lost.That is the case with any measurement. Counting can be exact, but any measurement is of limited accuracy. \>> What happens to the information between the time on the X >> axis? > > That is lost also.I have to disagree. Only information above half the sample rate is lost. (There better not be any anformation above half the sample rate. It would corrupt the entire signal with aliases.) Information about the entire continuous and properly sampled signal is retained in the samples. That's fundamental to digital processing.>> Someone told me that since the human ear can only hear >> frequencies up to 20kHz that sampling rates above this are >> unnecessary, but I don't buy it even though I can't put my finger on >> it.Sampling above 40 KHz is needed to reproduce 20 KHz. Some of the system needs to be analog (anti-alias prefilter and reconstruction postfilter). The higher the sample rate, the easier these are to build. ...>> I can't get it out of my head that digital representation of an >> analog signal is going to throw away some data.Sure, but so does any other system of representation and recording. It's not possible to copy something perfectly by any means. There are always losses, distortions, and artifacts.>> A finite >> representation of an infinite source. My audio soft/hardware offers >> sampling setups up to 96kHz and 32 bits per sample. It just seems to >> me that there is no limit to which one could push these numbers and >> still not reach the original.You can reach the limits of audible frequencies at sampling rates far below 96 KHz. You can exceed the accuracy of tape or vinyl with numbers smaller that 32 bits. There are four important points of comparison for audio: frequency response, dynamic range, signal-to-noise ratio, and distortion. Digital systems can match or outdo analog in all of them. Jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

Reply by ●April 15, 20072007-04-15

Tim Wescott wrote:> Ritual wrote:...>> What happens to the information between the single bit samples on the >> waveform? > > Information about voltages between the possible ADC output values is lost.That is the case with any measurement. Counting can be exact, but any measurement is of limited accuracy. \>> What happens to the information between the time on the X >> axis? > > That is lost also.I have to disagree. Only information above half the sample rate is lost. (There better not be any anformation above half the sample rate. It would corrupt the entire signal with aliases.) Information about the entire continuous and properly sampled signal is retained in the samples. That's fundamental to digital processing.>> Someone told me that since the human ear can only hear >> frequencies up to 20kHz that sampling rates above this are >> unnecessary, but I don't buy it even though I can't put my finger on >> it.Sampling above 40 KHz is needed to reproduce 20 KHz. Some of the system needs to be analog (anti-alias prefilter and reconstruction postfilter). The higher the sample rate, the easier these are to build. ...>> I can't get it out of my head that digital representation of an >> analog signal is going to throw away some data.Sure, but so does any other system of representation and recording. It's not possible to copy something perfectly by any means. There are always losses, distortions, and artifacts.>> A finite >> representation of an infinite source. My audio soft/hardware offers >> sampling setups up to 96kHz and 32 bits per sample. It just seems to >> me that there is no limit to which one could push these numbers and >> still not reach the original.You can reach the limits of audible frequencies at sampling rates far below 96 KHz. You can exceed the accuracy of tape or vinyl with numbers smaller that 32 bits. There are four important points of comparison for audio: frequency response, dynamic range, signal-to-noise ratio, and distortion. Digital systems can match or outdo analog in all of them. Jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

Reply by ●April 15, 20072007-04-15

> Ritual wrote:...>> What happens to the information between the time on the X >> axis? > > That is lost also.I have to disagree. Only information above half the sample rate is lost. (There better not be any anformation above half the sample rate. It would corrupt the entire signal with aliases.) Information about the entire continuous and properly sampled signal is retained in the samples. That's fundamental to digital processing.

Reply by ●April 15, 20072007-04-15

> Ritual wrote:...>> What happens to the information between the time on the X >> axis? > > That is lost also.I have to disagree. Only information above half the sample rate is lost. (There better not be any anformation above half the sample rate. It would corrupt the entire signal with aliases.) Information about the entire continuous and properly sampled signal is retained in the samples. That's fundamental to digital processing.

Reply by ●April 15, 20072007-04-15

> Ritual wrote:...>> What happens to the information between the time on the X >> axis? > > That is lost also.I have to disagree. Only information above half the sample rate is lost. (There better not be any anformation above half the sample rate. It would corrupt the entire signal with aliases.) Information about the entire continuous and properly sampled signal is retained in the samples. That's fundamental to digital processing.

Reply by ●April 15, 20072007-04-15

> Ritual wrote:...>> What happens to the information between the time on the X >> axis? > > That is lost also.I have to disagree. Only information above half the sample rate is lost. (There better not be any anformation above half the sample rate. It would corrupt the entire signal with aliases.) Information about the entire continuous and properly sampled signal is retained in the samples. That's fundamental to digital processing.

Reply by ●April 15, 20072007-04-15

> Ritual wrote:...>> What happens to the information between the time on the X >> axis? > > That is lost also.I have to disagree. Only information above half the sample rate is lost. (There better not be any anformation above half the sample rate. It would corrupt the entire signal with aliases.) Information about the entire continuous and properly sampled signal is retained in the samples. That's fundamental to digital processing.

Reply by ●April 15, 20072007-04-15

> Ritual wrote:...>> What happens to the information between the time on the X >> axis? > > That is lost also.I have to disagree. Only information above half the sample rate is lost. (There better not be any anformation above half the sample rate. It would corrupt the entire signal with aliases.) Information about the entire continuous and properly sampled signal is retained in the samples. That's fundamental to digital processing.

Reply by ●April 15, 20072007-04-15

Fred Marshall wrote: ...> However, that perfect situation doesn't happen very often. In fact the > statistically expected value / location for the input level is half way > between the digital levels. This means the average "error" will be 43.2/2 > or 21.6 microvolts in our example system.... Fred, Isn't the error half that? If the actual falls halfway between quantization levels *on the average* and sometimes hits a level exactly, then (with uniform distribution) it would sometimes be a whole level off. In fact, the maximum possible distance from a level is half an interval, so the average level must be a quarter. Your reply contained an attachment, a slide show of two pictures (two of them identical) Some of the pictures may have come from my website. One shows my snowy back yard in late morning light. What's the story here? Jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯