Having trouble recording structure-borne noise? Try this.
If you’ve got a persistent hum or low-frequency sound in your building, it gets very pervasive. Yet when you try to measure the decibels or record the noise, it’s hard to capture accurately. That’s probably due to the noise-cancelling microphones on many smartphones.
One workaround? Try plugging an external microphone into your smartphone. Soundproofist ran some tests on an iPhone and an Android, and compared two different decibel-meter apps. Using low-cost lavalier microphones, we attached them directly to the noise source and the path to record and measure the sound. As you’ll see in this video, we got mixed results for the decibel readings, but the lavalier microphones effectively picked up noise from the structure that’s barely detectable with just the built-in microphones.
Choose the right microphone
Most lavalier microphones are omnidirectional, which is a plus for this particular use. This type of microphone picks up noise from every direction, and it’s very sensitive. The downside of this is that it will also pick up room noise that’s not related to the sound you’re trying to capture: your voice, footsteps, and activities. So be prepared to stand quietly while you’re measuring. In these tests, Soundproofist used a Clippy EM272 lavalier from Micbooster, and a pair of iRig microphones from IK Multimedia.
Yes, you can use a cardioid lavalier microphone with a more-limited pickup pattern, but you’ll need to place it strategically on the noise path. For example, this cardioid microphone from Sonorous Objects in New York is often used by nature recordists, who need highly sensitive mics.
Your goals
Are you trying to accurately measure the decibel level of a structure-borne noise? You’ll see in this video that while the decibel reading reflects the decibels inside the building frame, it might appear louder than what a human ear can hear inside a room. Consider taking multiple readings to measure the room noise in different ways: with and without external microphones, directly on the noise path as well as the sound inside the room.
If you want to record the hum or low-frequency sound as evidence for your building manager or neighbor, an external mic can be really handy. In this video, you’ll see that you can measure and record noise simultaneously inside the SmarterNoise Pro app on Android. However, the iPhone app in this video (Decibel Meter) can measure decibels and frequency, but it doesn’t record the audio. You’ll need to use a different app to make an audio recoding, such as the built-in iPhone apps for video or audio. If we find an effective app that does all of these tasks at once, we’ll post it here.
Watch the video
This video shows some tests made with external microphones, including some errors and inconsistencies. We hope that you can successfully document your noise problem on a low budget, using easily available tools.
Learn more (including other people’s techniques):
- Soundproofist: A reliable Android app that measures decibels and noise
- Soundproofist: How to use smartphone apps to measure noise
- Auxiliary Sound (YouTube): “Field Recorder Setup Using Your Smartphone | 2022 Edition”
- Group DIY Discussion forum: Best way to record/measure structure-borne noise?
- Sciendo.com: “An engineering method to measure structure-borne sounds
transmitted through the building partitions” - ADASH engineering (YouTube): “Vibration analysis for beginners 4 (Vibration terms explanation, route creation)”