Kill The Noise

DATELINE: Now. On your system. Where you and other computer-based DAW users are reporting way too often that they’re hearing clicks and pops in their recordings and/or playback. Why?
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Well, there are several reasons this is happening, and when troubleshooting, it’s important to examine each possibility one at a time, keeping in mind that these problems can happen in just about any Mac- or PC-based DAW.

But let’s start by using MOTU Digital Performer 4.5 as our example.

First determine the source of the audio recording: Was the audio imported into the project from a CD or another type of audio file? If so, check to see if the noise is heard elsewhere with the same file — try it in your favorite music player, and maybe even a different computer.

If the audio was recorded directly to the system, check to see if the clicks and pops were recorded to the track. You can frequently zoom in to the waveform to look for spikes.

One of the most common causes of clicks and pops in recorded audio tracks is improper setup with digital inputs. Whenever sending a digital signal (ADAT optical, S/PDIF, AES/EBU, and so on) into a DAW, be sure to check clock settings. Typically, the recording system will want to reference the incoming digital signal as its clock source.

If the noise is already a part of the track or file, it may be difficult to remove the noise. A few simple “pops” might be removable, but lots of noise can be hard to separate. While there may be little you can do to fix recorded noise, it will help to know how to prevent it from happening again.

If it’s not clear that the noise is being recorded to the track(s), check to see if the noise is being added during playback. If your system is working too hard and can’t keep up with audio playback, noises, such as clicks and pops, may occur. Like DP4.5, most recording applications have a “performance” window or meter to indicate how hard the computer is working.

If the system shows that it’s under heavy strain, you may need to reduce the number of plug-ins, or bounce tracks (or groups of tracks) to disk (see September ’04 Tech Bench, “Managing CPU Power”). You can frequently reduce strain on your system by raising the hardware buffer size.

Playback noise could also be caused by a problem with the audio interface hardware you’re using. Try recording and playing back with different hardware. In our example with Digital Performer, users can select “Built-in Audio” to hear audio through the Mac’s speakers and compare it to the audio interface.

These are the most common causes of noise in recording software, so check for them first. Of course, there can be other causes of noise; bad or slow hard drives, mixers, speakers, and other components outside the system can all be culprits. Troubleshoot by eliminating one factor at a time until you can isolate the problem. And remember, patience.