The freeware GratisVolver™ continues to be one of the most useful applications that I own. The ability to convolve impulse responses with anechoic program material let’s me sit at the mic position and listen to what a room measurement sounds like in the comfort of my office. It is also a powerful tool for producing the room impulse response (RIR) from a sweep recording. I used it to produce the RIRs for our “Techny sessions,” which are among our top downloads ever. I’ve written much about this technique in the past. Here’s a link for our members.
The Need for Proper Relative Levels
A great tool just got better. The previous version always normalized the RIR to full scale. That’s pretty standard practice and not a problem when looking at a single measurement. But, I usually make log-spaced measurements that I want to compare later. At Techny I use 20, 40, and 80 ft. When these are normalized to 0 dBFS, the reverberant field level gets louder with increasing distance from the source and the direct field stays the same level. That’s just the opposite of what happens in a real room. I’ve always been able to mentally ignore this, but I no longer have to.
Calibration Support Added
The new GV adds calibrated RIR support. You can select the closest measurement as the reference, and the more distant measurements will be the correct relative level – great for showing how the direct field becomes swamped by reverberation with increasing distance from a source. The new version also adds some formatting options.
Lastly, there’s a new Techny session coming out soon. It will include RIRs of some small-format line arrays and Don Keele’s powerful CBT array. All of the RIRs were produced using – wait for it – GratisVolver™. pb