# The Audio Fool

• #### 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...
• #### 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...
• #### 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...
• #### 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 ...
• #### How to drive on Snow and Ice

Ah, the winter storms are upon us once again. And once again, a disproportionate number of my extended neighbors are demonstrating their incompetence behind the wheel. It seems that no matter how many times the Puget Sound region gets snowed upon, people...
• #### 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...
• #### Why is everything in audio measured in dB?

Short answer: Because the ear measures things in dB. The decibel is nothing more than a ratio between two numbers. (The unit was originally just a bel, but for audio it was more convenient to use tenths of a bel, hence the SI 'deci' prefix) Mathematically...
• #### 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...
• #### 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...
• #### 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...
• #### 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...
• #### The Rules of Code Optimization

Steve Rowe recently talks about who you're really writing for when you write code. The argument he makes is essentially that your primary audience is not the compiler, but rather your primary audience is other developers. This is something I believe strongly...
• #### 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...
• #### 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...
• #### Should you use Vista? I do.

I'm completely switched over. Aside from my two linux servers, every machine I run is on Vista, and the OS isn't even finished yet. Since Beta 1 we've been asked to "Self Host" - to run Vista on our primary development and productivity machines. On early...
• #### Categories of Legacy Applications

If you've used Vista, you've probably been exposed to the UAC dialog. It's the security dialog that pops up when the screen goes gray, and asks you permission to perform a task which requires admin-level elevation . The idea behind it is that once programs...
• #### 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...
• #### Audio Fidelity: Dynamic Range

I want to talk about noise for a minute. We all know what noise is, and that we don't want it in our audio. Unfortunately, noise is always present, whether we want it or not. In pseudo-technical terms, noise is random unstructured variations in a signal...
• #### Of ground axes and long suicide notes

There's been an " analysis " floating around the 'net in the last few days from Auckland University's Peter Gutmann about how Windows Vista DRM will destroy computing as we know it. The article's penultimate soundbite comes in its Executive Executive...
• #### 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...
• #### Youtube on the Loudness War

Larry pointed me to a really cool video that graphically and audibly demonstrates the effect of the Loudness War , and what happens to samples under excessive clipping. http://createdigitalmusic.com/2007/05/16/loudness-war-music-over-compression-demonstrated...
• #### And for my encore... Sleep.

As you've almost certainly heard by now, we've finished. Windows Vista has shipped , and our mantle has passed on to the manufacturers, who now have a little over two months to stuff a hundred million DVDs into boxes and put them onto store shelves everywhere...