Drawing the sound. Part 1
Hi! In the last article, I told you about the application of acoustic holography and SVS technology. Let’s move on. Now drawing sound!
In this series of articles, I will tell you what and how the SVS sound visualization system uses the spectrogram, how to choose the best frequency for analysis even in noisy environments, and I will tell you about the cases we solved.
Let’s get started :)
Physicists define sound as “an audible-perceivable physical phenomenon produced by the oscillating movements of particles of air or another medium.” For example, the tension of a guitar string.
Sound as a physical phenomenon is characterized by three parameters: pitch, force, sound spectrum.
What is a spectrogram?
A spectrogram is “an image showing the dependence of the spectral power density of a signal on time. In other words, a spectrogram is a graphical representation of sound.
A spectrogram can be formed in two ways: approximated as a set of filters or calculated over time using a Fourier transform window.
The usual representation of a spectrogram is a two-dimensional diagram: the horizontal axis represents time, the vertical axis represents frequency; a third dimension, indicating the amplitude at a particular frequency at a particular point in time, is represented by the intensity or color of each point in the image. Sources of intense sound are displayed in red, while quiet areas are displayed in dark blue.
For example, the image shows a spectrogram obtained when investigating the operation of the compressor by the SVS system. One of the elements emitted a characteristic knock (this knock is visible as a red band).
Why do I need a spectrogram?
Spectrogram allows you to understand ambient sounds. This feature can help with equipment troubleshooting and help optimize and improve equipment diagnostics. SVS needs a spectrogram for just this purpose. Want a taste of how a spectrogram works, see here. Real-time audio from the microphone is converted (just remember to allow access in your browser) into a spectrogram. When you click on the spectrogram, the app plays the sound with the appropriate pitch.
By analyzing the spectrogram of an audio file, you can see a chaotic image. For example, professional musicians use such images to analyze music and identify problem areas. New opportunities for steganography have opened up. Whole images are encoded into spectrograms. Some enthusiasts are taking advantage of this: the famous DJ Aphex Twin embedded selfies in this track in the form of a secret message displayed on a logarithmic spectrogram.
In the next article, I will tell you how to choose the frequency to analyze the sound environment.
By the way, ready to answer questions, write to @ni_meleshko.
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