I grew up in a musical family, and my dad always had this funny quirk about acoustics and echoes. If we entered a reverberant space, like a concert hall or a racquetball court, he would instinctively clap his hands and listen to the following echo.
I find myself doing those types of little things more and more as my life more tightly revolves around music with each passing year. What my dad was doing was actually very relevant to the current topic of DSP (digital signal processing) and modern advancements in sound recording.
With his clap, he was creating what recording engineers call an impulse response. The impulse is the quick, striking force of his hands together, and as a short sound, it gets out of the way quickly and lets the longer echo of the clap reverberate around the space.
Musicians have been sampling sounds of instruments for many years — snare strikes and kick drum samples show up in most hip-hop and pop music in some form.
But more recently with the increasing power and decreasing cost of DSP, samples of reverberant spaces have become a common recording tool. The idea is that someone else records an impulse — a clap or electric spark or balloon pop — in an echo-rich environment, chops out the impulse sound and makes available for your download the resulting echo. Then you can plug the sound into what's called a "convolution reverb" program which will allow you to apply the echo to anything you wish.
This is DSP hard at work, as the process requires complex computation. The result is that you, in your carpeted bedroom with no sound treatment whatsoever, can make it sound like you're playing guitar on stage at Red Rocks.
DSP is just the processing tool, and possibilities for its application are only limited to the imagination of developers. For example, Ocean Way Recording, a famous studio in L.A., has its own convolution reverb program that takes the process up a notch. The Ocean Way app is so extensive in scope, you can not only "position" yourself all over its famous recording rooms and hear what it would sound like if you were actually playing in that spot, but you can also hear the echo and music through the sonic character of many famous vintage microphones using their Microphone Locker app.
The beauty of convolution reverb is that none of it is algorithm or theory-based. These are the real sounds of real places, and when your brain hears the echo, it knows it's a real space. The brain computations that take place to process sound are staggering, and as time goes on, scientists have been getting better at synthesizing real sounds accurately. But there is no substitute for real sounds to the human brain.
The use of DSP is reinvigorating older instruments as well. Pipe organs, through the project Hauptwerk, are being sampled in their own environments now. If you've got a good pair of headphones and a MIDI keyboard, you can play Toccata and Fugue in D minor in the Mormon Tabernacle. Amazing.