【實用教育app】Frequency Dragon|最夯免費app-綠色工廠好玩App

Frequency Dragon generates frequency sweep signals, or fixed frequency signals and play the signals while recording.

It helps to find resonance frequency for concave objects or musical instruments.

The first step is generate the sweep signal, for example from 0Hz to 4000Hz.

Second step is put your android device inside the resonant object and press measure button.

You have the results in time and frequency.

It can play multiple times the signal and show the frequency response for each play.

Basic steps:

1. GENERATE; in a place without noise (silence) select start and end frequency, press GENERATE button.

2. MEASURE: position the smartphone , select the delay time and press PLAY button, under PLAY button you can see the graph that shows the differences between the original signal and the signal you are reading, Resonance should amplify the signal for some frequence and you should see this difference. if you configured multiple reads, the graph mediate each read to remove background noise.

3. FFT: view the reading in the frequency domain,you can send the results by email.

Note: Many devices does not have mic gain control, you can reduce sweep amplitude in config page for the output signal, but some devices mic gain is very high and sine waves generated by device speakers become square wave from device mic, this makes frequency analysis useless.

Max frequency should be less than 1/3 of the sample rate.