Frequency Tracer

Accurately measures one frequency in Hertz with frequency range up to 4000Hz. The accuracy can reach 0.1mHz depending on the noise level. The app will also display the trace for this one frequency and its amplitude. The traced frequency can be the largest peak or first harmonic (pitch). The possible use cases include a Guitar Tuner, Singer tracing its vibrato, All types of instrument tuning, vibration tracking in machinery and any other signals that you can wire in to your phone within the specified frequency range.

Testing the frequency accuracy

The 0.1mHz claimed accuracy can be tested with a simple tone generator running on another device. Set the frequency resolution to maximum at 0.125Hz and enable the 3s long time window. On first attempt, you might get a value, which is 0.0030Hz off the target. Then apply additional correction of the sampling frequency for example to 44100.3 Hz on the settings page depending on your specific situation, if you are over or under shooting. This should get you very close to 0.1mHz sustained average error. If you now change the frequency in your tone generator, the error in % should persist across the entire frequency range.

Selecting the frequency resolution

The higher the frequency resolution, the higher will be the accuracy of the measurement. The highest resolution is 0.125Hz and this will need a stable frequency within a 4second long window. Sometimes the frequency is not stable for 4s and that is why lower frequency resolutions are available. The length of the analysis window will get shorter with lower resolutions. The resolution of 1Hz, needs 0.5s long time window to perform the analysis.

Measuring the amplitude

Provided that the frequency is stable enough, extremely minuscule and accurate amplitude changes can be detected as well. The amplitude measurement allows for user correction with Offset and Scale parameters.

Again, here you could use an external (calibrated) device, to obtain a reference for specific sound pressure or voltage level.

Pitch detection and pitch standard

The application also has a configurable pitch standard with default set at A440 Hz. When in Hungary modify this preset to A442 Hz. The pitch detection algorithm has two modes of operation: largest peak and first harmonic. The app can detect multiple harmonic series, but it will favor the the harmonic series with the fundamental, that has the lowest frequency. If you have an instrument with known ratio between individual harmonic series, and the pitch does not equal lowest fundamental, you could still calculate the pitch.

Duration of the history window

The history window will provide a trace of frequency variations of the largest peak (fundamental) and its amplitude. This trace is used to compute the average frequency and average amplitude together with 95% confidence interval. The 95% confidence interval is displayed in the label following the +/- sign. Longer history window will allow greater precision. However greater precision mostly depends on how stable this frequency will be during this time window. With some musical instruments, this time depends on how long you hold the key, but with piano for example, this time is finite and the analysis window may not exceed the duration of the tone.

Setting the threshold

You can configure the start of the measurement by setting a threshold, the minimum amplitude level or loudness, at which the measurement will start. When the amplitude of the traced frequency drops below this level, the measurement will stop. You can see the currently detected amplitude level on the amplitude display.

About this application

This software uses propriety algorithms developed by the owner Company, which were never published. A purchase of this application includes a limited best-effort warranty, that the application will perform as advertised.