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Voca is a speech and audio viewer that can be helpful in speech therapy and education. Voca displays the sound coming into the microphone graphically on the screen. Available viewing option are: spectrogram, frequency display, waveform and audio volume history. This tool is useful for encouraging speech and seeing different patterns generated by different sounds.
Sound traces and images can be easily captured to your device photos.
Voca contains no adverts and does not require a subscription. There is a demo on the website link, which should work in Safari.
Voca is not a calibrated sound measuring device, but shows waveshapes, waveforms and short term time traces.