Spectrograms
Introduction
A spectrogram illustrates how the constituent frequencies of a signal vary over time. This application
generates the spectrogram of several audio files, including a• DTMS tone,• human voice saying “MapleSim”,• violin note played with vibrato, and an entire violin scale,• C8 piano note,• series of dolphin clicks,• and more.
Interestingly, some electronic musicians hide images in their music; you can only view these images with aspectrogram of the appropriate part of the audio. This includes the track “My Violent Heart” by the Nine
Inch Nails; you can view this spectrogram in this application.
The Spectrogram function was introduced in Maple 18, and also lets you plot the waveform and powerspectrum> restart :> with SignalProcessing :Violin> f1 d AudioTools:-Read "Violin_for_spectrogram.wav" :A series of notes> Spectrogram f1, colorscheme = "SteelBlue", brown, "white", "black", red , fftsize = 512, reduceplot= 0, view = 0 ..5, 0 ..10 , size = 800, 400

A single note played with vibrato> f2 d AudioTools:-Read "ViolinThreePosVibrato.wav" :> Spectrogram f2, colorscheme = "zgradient", white, LightBlue, red, black , markers = 0, 0.5, 0.75,
101 , fftsize = 2 , channel = 1, size = 800, 400

Human Voice> f3 d AudioTools:-Read "maplesim.wav" :> Spectrogram f3, colorscheme = "zgradient", white, LightSteelBlue, black , markers = 0, 0.5, 1 ,fftsize = 256, size = 800, 400

Engine Shifting Gears> f4 d AudioTools:-Read "car3.wav" :> Spectrogram f4, colorscheme = "zgradient", white, LightBlue, red, green, black , markers = 0, 0.25,0.5, 0.75, 1 , fftsize = 2048, channel = 1, size = 800, 400 , view = 0 ..5, 0 ..5

DTMF> f5 d AudioTools:-Read "DTMF.wav" :> Spectrogram f5, colorscheme = "zgradient", white, grey, black , markers = 0, 0.5, 1 , fftsize = 256,size = 800, 400

Ding> f6 d AudioTools:-Read "ding.wav" :> Spectrogram f6, colorscheme = "zgradient", white, grey, red , markers = 0, 0.5, 1 , fftsize = 512,size = 800, 400

Dolphin Clicks> f7 d AudioTools:-Read "dolphin.wav" :> Spectrogram f7, colorscheme = "zgradient", white, grey, SteelBlue, black , markers = 0, 0.5, 0.85,
1 , fftsize = 256, size = 800, 400 , channel = 1, view = 0 ..0.7, 0 ..4

1KHz Wave
Note that the spectrogram and power spectrum both identify a peak at 1 KHz> f8 d AudioTools:-Read "1khz.wav" :> Spectrogram f8, colorscheme = "zgradient", white, black , markers = 0, 1 , fftsize = 512, size
= 800, 400 , view = 0 ..0.7, 0 ..4 , includepowerspectrum

Power (dB)3020100K10K20
K30
K40
K50K6012Frequency (kHz)34Wilhelm Scream> f9 d AudioTools:-Read "wilhelmscream.wav" :> Spectrogram f9, colorscheme = "zgradient", white, SteelBlue, black , markers = 0, 0.85, 1 , fftsize= 512, size = 800, 400 , view = 0 ..0.7, 0 ..4 , channel = 1

Piano Note C8
Should have a frequency of 4186 Hz> f10 d AudioTools:-Read "pianoFF_C8.wav" :> Spectrogram f10, colorscheme = "zgradient", white, SteelBlue, black , markers = 0, 0.9, 1 , fftsize
12= 2 , size = 800, 400 , view = 0 ..0.25, 4 ..5 , channel = 1

Nine Inch Nails
An image hidden in a spectrogram of the song "My Violent Heart" on the album "Year Zero"> f11 d AudioTools:-Read "nineinchnails.wav" :> Spectrogram f11, colorscheme = "zgradient", white, SteelBlue, black , markers = 0, 0.5, 1 , fftsize
9= 2 , size = 300, 400 , reduceplot = 1, axis 2 = mode = log , view = 0 ..2, 0.2 ..15

Compare to the "Year Zero" album coverMapleA message hidden in a spectrogram...
> f13 d AudioTools:-Read "maple.wav" :> Spectrogram f13, colorscheme = "zgradient", white, SteelBlue, black , markers = 0, 0.5, 1 , fftsize
11= 2 , channel = 1, view = 0 ..5, 0 ..3>