Low Frequency Detector 4+


    • $9.99

iPhone Screenshots


"Low Frequency Detector" is a new acoustic measurement tool for detecting the low frequency sound that is hard to hear in the normal situation.

The human ear is insensitive enough to become a low frequency. If you may be exposed to the noise of neighboring constructions and factories without noticing, you may have a feeling bad and a sense of oppression. In this case, you can check what type of low frequency noise exists by simple operation of this app.

In general, the low frequency sound is a sound wave with 1 Hz to 100 Hz. By depending on its frequency component and sound level, it is different the degree of influence on the human body and the noise sensation.

This app also allows you to examine the frequency component of the low frequency sounds by 1/3 octave band analysis and FFT analysis.

- Low frequency power level measurement less than 100Hz (LF Level): Flat characteristic, Updating indication of measurement period 1 sec.
- Power level measurement in the audible band (Leq): Flat characteristic, Updating indication of measurement period 200ms.
- 1/3 octave band analysis (OCT)
- FFT analysis (FFT)
- Time course graph (TIME)
- Snapshot (Snap) on the measurement display screen.
- Report function (Report): Analysis report of a peak LF Level with TIME, OCT and FFT.
- Measurement time : up to 60 sec.

The measurement analysis is performed in the following step. Be sure to set the measurement conditions in Step-1 once before starting the sound measurement.

1) Calibration (Calibrate): A reference signal (1kHz sine wave) is output to determine the reference noise level for the low frequency component. If the volume level of iPhone is set to about 20-50%, the calibration will automatically adjust it to the optimum volume level for the reference signal.

2) Measurement (Measure) : Analyze a power level of low frequency sound.
- LF Level (dB): Low frequency power level less than 100Hz.
- Leq (dB): Sound power level with the frequency weight characteristic Z (Flat) of the audible band.

3) Measurement display: It can select either 1/3 octave band frequency analysis, FFT analysis or Time course graph. They are updated in real time.

4) Report: Measurement result report. It is effective when measuring for 10 seconds or more.
# Time course graph : TIME
- Low frequency (LF) Level (dB): Time course graph with peak level noise level judgment (RED-very noisy, YELLOW-noisy, GREEN-normal) at the peak level.
- LF max (dB) : maximum dB value of low frequency.
# Frequency response graph : OCT, FFT
- OCT Band LF max (dB): maximum dB value in 1/3 octave band at LF max observation.
- Max Level Frequency (Hz): peak frequency at LF max observation.

- The sound measurement of the low frequency range is a level difference with respect to the reference signal (1kHz sine wave), which indicates the relative power level.
- The reference signal is output during calibration and sound level measurement.
- Do not change the volume level of iPhone after the calibration.
- White line in the OCT and FFT modes indicates frequency characteristics in frequency weight correction of G characteristics.
- Since iPhone's built-in microphone has a lower sensitivity on the very low frequency range, it is not recommended to measure a huge volume sound near a very loud noise source.
- Since it takes a while for the observation value to stabilize immediately after the start of measurement, the maximum value is calculated from about 2 seconds later.
- In the case high power of 1kHz component is included in the measured noise source, the precision of measured value by this app largely decreases.
- Sudden noise or impulsive sounds are not low frequency noises in general.
- The previous calibration information can be maintained internally.
- The analysis results may vary due to individual differences in iPhone devices.
- The authorization to access built-in microphone and Photos will be confirmed by iOS system at first boot.

What’s New

Version 5.0

- Improved internal processing and performance.
- Renewed UI design.
- Requires iOS 15.0 or later.

Ratings and Reviews

3.2 out of 5
5 Ratings

5 Ratings

thisnicknameistaken-1 ,

Pretty good

This app isn’t as intuitive as other noise detection apps. You have to tune it first by adjusting the volume on your phone, as it sends out a reference signal. The other thing that is not intuitive is it doesn’t show you a live readout of decibels versus frequency like some of the other apps. You have to essentially push “record” and it takes a reading over 60 seconds, then push another button to get the report.

I’m giving it four stars though because it seems pretty accurate. When I’m sensing my neighbor’s bass, it reflects in the report as well (the report shows you the decibels versus frequency and is color-coded to reflect low, medium, or high noise levels), and when I’m not sensing it, it reflects that too.

M22222299999 ,

Very useful and it works

This app had a slight learning curve, but it’s well designed to lead one through what to do. It’s easily well-calibrated enough for my purposes, and getting it to work with the tiny iPhone mic was ingenious. Extremely worth the value. Update: I realized after I wrote the above that it almost looks like a fake review. I’m a meditator who is very sensitive to sound in the environment. LF sound is hard to localize, but I was able to use this app, in addition to my other senses, to walk around and eventually find many intermittent LF sources in my vicinity, made easier by the multimodal sharp peaks in the FFT when I got closer to and farther from different sources.

Robertdmc ,

Works best between 30 Hz and 110 Hz

It cannot detect 120 Hz or above because it is outside the range, and 20 Hz and below seems to get lost in the background noise. Both 30 Hz and 110 Hz are detected.

App Privacy

The developer, TOON,LLC, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy.

Data Not Collected

The developer does not collect any data from this app.

Privacy practices may vary, for example, based on the features you use or your age. Learn More


  • Family Sharing

    Up to six family members can use this app with Family Sharing enabled.

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