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You can't hear DC
Recently one of my team members found a bug in some old code while doing a code review. Our application was generating a sine wave to be rendered by the audio hardware. The sample format isn't important except to note that it is an unsigned value between Read More...
Posted 21 June 07 10:00 by RyanBemrose | 4 Comments   
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More posts eventually!
It's that time of year, it seems. I was down with the flu last week, and I'm trying desperately to catch up this week. I promise I'll get more posts up soon. I'm doing some WASAPI playback library stuff right now and I'm just dying to do a couple of articles Read More...
Posted 05 March 07 06:09 by RyanBemrose | 6 Comments   
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Digital Audio: Aliasing
Sampling a continuous waveform into discrete digital samples results in lost information. Discrete samples can only tell what the wave is doing at periodic instants in time, and not what's happening between them. The continuous sampled wave could be doing Read More...
Posted 15 February 07 08:26 by RyanBemrose | 2 Comments   
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Clipping in popular music
Aside from the distortion artifacts, one of the biggest problems that results from clipping is a loss of dynamic range. Remember that the dynamic range of a signal is effectively the difference between the maximum output level and the noise floor . When Read More...
Posted 07 February 07 02:44 by RyanBemrose | 5 Comments   
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Louder Sounds Better
Below is an example of the Fletcher-Munson Equal Loudness Curve . It is one of the most recognized graphics in audio engineering. The horizontal axis is frequency of tones, and the vertical axis is actual sound pressure in dBSPL. Each point on a curve Read More...
Posted 07 February 07 02:12 by RyanBemrose | 2 Comments   
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Audio Fidelity: Clipping
In theory, an audio signal can take on any amplitude. There is no mathematical upper limit for how far from zero a sample can go, or how high the magnitude of a continuous wave can go. In practice, however, a digital signal's amplitude is limited by its Read More...
Posted 09 January 07 02:30 by RyanBemrose | 5 Comments   
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The difference between measuring DR and THD+N
I've talked here before about how noise and distortion are very similar concepts with very different causes. Noise is unwanted artifacts independent of the signal often caused by physical processes outside of a device. Distortion is unwanted artifacts Read More...
Posted 06 December 06 05:49 by RyanBemrose | 1 Comments   
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Audio Fidelity: Output Level
Output level is one of the simplest fidelity metrics to understand, but don't take that to mean it's not important. There are several occasions where you want to know the maximum, loudest value that a signal can get. On the digital side, that's pretty Read More...
Posted 04 December 06 10:10 by RyanBemrose | 1 Comments   
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Always dither before you quantize
Quantization adds noise. Taking a nice continuous signal and expressing it as distinct integers will introduce a round-off error, which means you've added random fluctuations to the signal, which is the definiton of noise. Remember that noise is inevitable Read More...
Posted 18 October 06 01:07 by RyanBemrose | 2 Comments   
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Audio Fidelity: Frequency Response
Not all frequencies are created equal. And they're also not generally treated equally by a digital filter. How inequally they're treated is one of the defining characteristics of a filter. Audio engineers have a metric for describing this behavior. The Read More...
Posted 20 September 06 06:00 by RyanBemrose | 2 Comments   
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Audio Fidelity: Crosstalk
For years, recorded audio was just a signal, captured by a microphone, stored as an audio signal, and then played back by a speaker. The microphone acted as a "proxy" eardrum to hear the sounds when and where the real listener's ear couldn't be. But somebody Read More...
Posted 01 September 06 07:18 by RyanBemrose | 2 Comments   
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32 bit audio redux
In my previous post , I don't think I explained very well why a 32-bit signal wouldn't work on the low-end. The point, I think, was well-taken on the high-end. You don't want a 192 dBSPL audio signal applied to your body (or your planet, for that matter). Read More...
Posted 23 August 06 04:44 by RyanBemrose | 9 Comments   
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A Lesson in Dynamic Range (or Why 32 Bits per Sample Should Never Catch On)
Anywhere you go, you will be able to find people who will insist that more is better. Bigger cars, larger portions, and more bits in your audio samples. But we thinking people know that there is such as too much of a good thing, don't we? I refer, of Read More...
Posted 22 August 06 07:19 by RyanBemrose | 11 Comments   
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Quantization, Sample Rate, and Bits Per Sample
Forgive my digression, but I need to lay some digital signal processing ( DSP ) groundwork for what I want to talk about next. If you're already a DSP guru, then you may want to skip this one. (If you're a DSP guru, what're you reading a blog called "Audio Read More...
Posted 16 August 06 11:28 by RyanBemrose | 3 Comments   
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Audio Fidelity: Distortion
Distortion in audio is very closely related to noise. Both "distortion" and "noise" are used to describe unwanted components of an audio stream, so what's the difference? I already defined noise when I talked about dynamic range . But what is distortion? Read More...
Posted 07 August 06 09:40 by RyanBemrose | 3 Comments   
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