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Sorry for the horrible title!

I'll cut to the chase... I have a noisy neighbour and hear a lot of 'Impact Sounds', I believe the frequencies are < 100 Hz.

The council advised me to use 'The Noise App'. I made a short video, and hopefully you guys can makes sense of what I'm trying to demonstrate here. Just Off-Camera, I am banging a wall and there is a deep thud / boom sound (replicating the sounds I hear from my neighbours) - Decibel X shows up to 70db, while The Noise App records nothing.

This is annoying as I submit my 'evidence', they then listen to it (through what equipment, I am unsure) and hear nothing, in turn saying there is no noise.

How can I simply explain to them (without coming across as condescending) that The Noise App is not adequately recording these sounds, while you can see there is sound when referencing the SPL.

Hope you guys understand where I'm coming from.

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    I'm voting to close this question as off-topic because it should be directed to the noise app support department.
    – audionuma
    Feb 13, 2018 at 16:51
  • Did you make sure the microphone permission on the ipad was allowed?
    – Timinycricket
    Feb 14, 2018 at 9:51

3 Answers 3

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Assuming that your app is working at all, the most likely explanation is that the microphone circuit in your tablet contains a high pass filter (a filter which removes low frequencies). This means that the sounds that are bothering you, which are low in frequency, will be recorded as much lower in level than they actually are in reality. You may be able to overcome this with a quality external mic. Or, since the phone seems to pick up those frequencies, use it for your recording device.

I should add that SPL meter apps that run on phones are generally not accurate unless they have been calibrated using a commercially calibrated SPL meter as a reference. Even then, you can't expect perfectly accurate SPL numbers at all frequencies because phones aren't designed for accurate frequency response, they are optimized for voice frequencies.

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  • Thanks. I would like to add that its not the device per-se. I could run these two apps the other way round (i.e., The Noise App on the iPhone) and the results are the same.
    – Jimmy
    Feb 13, 2018 at 13:57
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    Then there's something wrong with the app or its settings.
    – little_birdie
    Feb 13, 2018 at 15:11
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Judging by your recording I don't think your banging is reaching 70dB SPL.

A normal conversation speaking level is 60dB. That being said a HPF would also dampen the sound even further.

https://www.thenoiseapp.com/#/technical

According to their website they are able to bypass the high pass filter after a certain iOS (9.2.1) but also states that it has limitations recording frequencies <200hz which is basically where the HPF would be set so... my conclusion is that you are trying to record too low of frequencies at too low a volume.

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The massive difference between the two measurements could be probably due to the time averaging:

See the article below: (Section Equivalent continuous sound level) https://en.wikipedia.org/wiki/Sound_level_meter

To check this, try to find a continuous loud source of noise (maybe your car engine or a lawnmower) and compare the two.

If they agree more closely with continuous noise then this is the problem

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