NoiseCapture App

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Contact - noisecapture[at]noise-planet.org
Web - http://noise-planet.org

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Introduction

NoiseCapture App is an application dedicated to the evaluation of your noise environment. It allows to perform measurements and, thus, to give information on your noise exposure. In addition, you can contribute to the realization of collaborative (or community) noise maps by anonymously sharing your measurements.

Main steps:

  1. Start a measurement
  2. Give a description
  3. Analyze results
  4. Explore the map

Additional steps:

Go further:

NoiseCapture App is an application, made by experts, but do not forget that it will never replace a professional sonometer. If you need a professional assistance, please contact a specialist.

The quality of the measurement depend of the technical performance of the smartphone. Depending of the smartphone and the android version, some smartphone may produce bad estimation of the sound level. See section concerning the limits of noise measurement with a smartphone for more information.

Start a measurement

On the Measurement menu item, press the RECORD button to start a measurement. You can stop the measurement by pressing the STOP button.

You can pause/resume a measurement using the PAUSE button. Depending on the corresponding Settings value, when resuming the measurement, the last seconds of the measurement can be removed.

What is displaying?

Give a description

On the Description menu item:

This step is optional but it could be useful to evaluate the noise environments, as well as for a research purpose. Your contribution will be highly appreciated. Only the anonymous elements 'Pleasantness' and 'Tags' are uploads. The 'Description', as well as, the 'Picture', are stored on your smartphone only and, thus, not uploaded.

Analyze results

On the Results menu item, you can access to several noise indicators.

While during measurements sound level are displayed in a 'fast' mode (125ms), final results are given in a 'slow' mode (1s), based on the 1s (one second) equivalent sound level (Leq,1s). Leq,1s is a standard environmental noise indicator, used for the evaluation of noise annoyance.

What is displaying?

Explore the map

On the Map menu item, users can access to a geo-referenced representation of the measurement that are stored in the smartphone memory. Users can choose to represent:

Explore the measurement history

On the History menu item, users can access to all measurements that are stored in the smartphone memory.

All measurement that are performed with the smartphone are archived in the history. You can access to the state of the measurement ('Upload' or 'Not upload' to the server) with the 'Cloud' symbol,

By tapping on item from the history, you can:

If a measurement is removed from the history, but was previously transferred to the web server, it is not removed from the web server. Remember that all data that are uploaded to the server are anonymized; thus, be confident! (see Privacy)

Calibrate your smartphone

On the Calibration menu item, users have the opportunity to calibrate their smartphone.

Several calibration methods are available:
  1. Manual calibration from a reference device or a calibrator
  2. Manual calibration from a calibrator device
  3. Automatic calibration from a calibrated smartphone

The smartphone calibration is a crucial and necessary step. Without calibration, you can be sure that the measured data will be wrong!

The correction factor is applied for the whole signal. Multi-frequency calibration is not possible for now.

The calibration is carried out with dB values, not dB(A).

The correction factor can also be set manually in the Settings menu.

When using a 'Global' value for the calibration, make sure that the Reference value will be obtained using the same frequency range that your smartphone.

The 'Calibration warm-up time' and the 'Calibration duration' can be modified in the Settings.

During calibration, the smartphone and the reference device must be used in a similar way.

Calibration from a reference device

Calibration with a calibrator

To apply this calibration procedure, you need an acoustic calibrator and an external microphone. The diameter of the microphone should be compatible with the calibrator.

Automatic calibration from a calibrated smartphone

In this method, a smartphone already calibrated with NoiseCapture, can calibrate one or more smartphones. On the side of the microphones to be calibrated, the procedure is fully automatic. The entire system is controlled by the reference smartphone.

  1. The reference smartphone must be in "transmitter" mode.
  2. The smartphones to be calibrated must be in "receiver" mode.
  3. On the reference smartphone:
    1. Select the source signal:
      1. "Pink noise": in this case, the smartphone generates a reference signal. It is necessary to use a sound source connected wirelessly with the reference smartphone, the source being at equal distance from all smartphones;
      2. "Ambient noise": Environmental noise is used for calibration. The sound level must be sufficiently high and the sound field must be relatively "diffuse".
    2. Press Start; the rest of the procedure is automatic. You can cancel the current calibration with the Cancel button.

What are the limits of noise measurement with a smartphone

Device requirements for Android compatibility

The Android Compatibility Definition Document (CDD) "enumerates the requirements that must be met in order for devices to be compatible with the latest version of Android. To be considered compatible with Android, device implementations MUST meet the requirements presented in this Compatibility Definition" ( text from Android 5.1 CDD).

According to the CDD:

In addition, it is specified that " While some of the requirements outlined in this section are stated as SHOULD since Android 4.3, the Compatibility Definition for a future version is planned to change these to MUST. Existing and new Android devices are very strongly encouraged to meet these requirements, or they will not be able to attain Android compatibility when upgraded to the future version."

What does it theoretically means?

Thus, the quality of the noise measurement:

In conclusion, in the current situation, even after a rigorous calibration and without any further correction, it is not possible to ensure the quality of the measurement for low and high noise levels, as well as, beyond 4000Hz, whatever the device and the Android version. One can however assume that next smartphone generations should ensure a better measurement quality.

Best practice for the best noise measurement

In order to perform a correct noise measurement:

In addition, if you want to produce noise measurements that will be very useful for producing collaborative (outdoor) noise maps, please check these points:

Resources