Get rid of noise, hum, and hiss in your recordings—the overall sound will be so much better
Thankfully, tape hiss is in the rearview mirror for most of us. But that doesn’t mean that noise is gone completely from our lives. Now that we have gear with 24-bit resolution and noise floors that hit theoretical minimums, any noises are no longer covered up by something else and instead are exposed in all their ugly noisiness. So what can we do?
Well, plenty. But first, there’s no “silver bullet” for guaranteeing a noise-free recording. Every little extra dB of noise, distortion, or coloration adds up, especially if you’re into using lots of tracks. The solution is to carve away noise wherever possible, no matter how minimal, to keep all those little noise bits from multiplying—so here are some proven techniques to help in your quest for quiet recordings.
Mics and Mic Preamps
Unless you get into a boutique, stratospheric price range, modern-day mic preamps (even those with relatively inexpensive interfaces and mixers) are seldom the issue with noise—concentrate on the mic itself. The Self Noise spec, which is usually A-weighted, tells how much output the mic produces from a sound at a specific number of dB SPL. For example, RØDE’s NT1-A condenser mic has an extremely low Self Noise spec of 5 dB (A-weighted); it’s included in the recording-ready, NT1-A Complete bundle (Fig. 1).
Large-diaphragm mics tend to have lower noise than small-diaphragm condenser mics, and solid-state preamps in condenser mics are usually quieter than tube preamps (sorry, tube fans!). Granted, mic noise won’t be a factor if you’re using it only to capture a track from the lead singer in the punk band Snot Puppies of Doom, but if you’re recording twelve tracks of acoustic instruments played gently, you’ll hear a difference.
Background and Ambient Noise
It’s amazing how much ambient noise creeps into a studio—which you find out only after you do acoustic treatment, then walk into the room and realize that you’re surrounded by silence. Although you can put up individual panels as needed, it can be more economical to bite the bullet and get a complete acoustic treatment package, like the Primacoustic London-16 (Fig. 2) or Auralex ProPanel ProKit-1. However, if money is tight, trying a 24-pack of Auralex Wedgies for spot treatment of your room’s problem areas can make a worthwhile improvement.
Unwanted Audio Other than Noise
There are other audio issues that detract from your tracks, like vocals reflecting off untreated walls, which adds a “shadow” to your vocal. sE Electronics’ Reflexion Filter (Fig. 3) can help with that because it traps your vocal before it disperses throughout a room.
Note that mic placement within the filter is important to avoid coloring the sound; you want it within the reflector’s arc, but as far as possible from the filter’s rear wall.
Another option for some home studios is if there’s a closet near where you record. All those clothes can help diffuse/absord a lot of sound, although you’ll likely still need to add acoustic treatment to the ceiling and exposed wall surfaces.
Crackles: Even Worse than Hiss
Use contact cleaner, like Caig Labs Deoxit DN5, on your patch cord plugs, jack contacts, and controls. Tiny crackles can be masked during the recording process by everything else that’s making noises but may show up while under scrutiny during playback. In a worst-case situation, the surfaces of dissimilar metals may have actually started to crystallize. Not only can that generate noise, but these crystals are all potential miniature crystal radios, which can turn RFI into audio that gets pumped audio into the connection. Not good.
Not that we make any misstakez, of course, but do make sure any unnecessary mixer channels are muted when you record. Every unmuted channel is another potential source of noise. Also, use proper gain-staging to keep signal levels up, and noise levels down.
The Heavy Artillery
No matter how hard you try, some noise is going to make it into your recorded tracks—and you’ll need to clear it up after the fact. That’s when it’s time to bring out the heavy artillery, and iZotope’s RX7 (Fig. 4) is the gold standard for noise reduction, repair, and restoration software.
Even the least expensive version, RX7 Elements, can help remove noise, clipping, and clicks, amp hiss, room rumble, and more. RX7 Advanced is expensive, but if you do pro-level post-production, surround work, or narration, it can be a life-saver—it can even remove lavalier mic “rustling” noises, change the intonation of dialog, and isolate dialog from noisy backgrounds. It’s basically applied magic. The middle “standard” offering, RX7-IZO, does everything Elements does but also includes features like mix rebalancing, adjusting time and pitch, doing spectral repair (yes, you can probably remove that one cough in the middle of a live performance), and eliminate mouth clicks from narration. It’s pretty amazing.
If you plan to use noise reduction software to get rid of issues like hiss or hum, make sure you don’t trim tracks right up to the beginning or end of the audio. You want some space that’s pure noise so that the software can identify it, and subtract it from the track as a whole.
An Ounce of Prevention…
So is all this effort worth it? I think you’ll be pretty surprised when you hear what happens to a mix when the noise contributed by each track is gone. Minimizing even low-level noise can lead to a major improvement to the final sound…it’s almost like removing the dust from a fine piece of art.