After I posted my report on the Naiant X-R hypercardioid mic, which I’m using as a mandolin mic, my friend Dan Richardson wrote in to ask a question about how well it handles RF interference.

Dan’s a great audio engineer whose domain name, www.NotTooLoud.com, encapsulates much of what I appreciate about his work. Let’s do another gig soon, Dan!

Dan writes:

I’d be interested to know how it fairs hanging out near an iPhone that’s pinging a tower. grounding & rf shielding is a hard part to get right. Listen to the mic at performance volume while you take a cell phone out of airplane mode & send a text.  [snipped by me] listening somehow, just get a sense of the relative level of any interference you might pick up.

I don’t have an iPhone, but I decided to try it with my Android phone. I set the mic with the same gain settings I used in the tests I posted in the main article, and I placed the mic parallel to the long axis of the phone with the windscreen touching the phone. In the real world, I would never have a phone that close to the mic, but it seemed like a good idea for a “torture test” to see how much interference we could pick up.

Microphone test parameters

• Phone: HTC Rezound
• Location: Potsdam, NY
• Mic: Naiant X-R hypercardioid
• Audio interface: Presonus Firestudio Mobile
• DAW: REAPER64
• Audio processing: normalize track volume.

I started the recording with the phone on Airplane Mode. When I spoke, I was about a foot behind the mic, so my voice was in a pretty weak part of the mic’s pickup pattern. I turned off Airplane Mode (turning the phone’s radio back on), let it negotiate a signal, then sent a text message.

When it’s normalized, there’s definitely some interference going on there. Looking at the VU meters in REAPER, I found that the voice peaks at -1 dB, the Airplane Mode interference hangs out around -38 dB but spikes briefly up to -24 dB, and the sending-text interference averages -32 dB but spikes up to -23 dB.

This is a “torture test” in a number of ways, so I’ll bow to others’ experience on what these sounds and numbers mean in real-world effects on stage.