Dynamic spectrum using plotly

Question

I want to plot time vs frequency as x and y axis, but also a third parameter that is specified by the intensity of plot at (x, y) rather (time, frequency) point. [Actually, instead of going up with third axis in 3D visualisation, I want something like a 2D plot, with amplitude of third axis governed by the intensity(color) value at (x,y)].

Can someone please suggest me something similar that I am looking for? These plots are actually called dynamical spectrum.

PS: I am plotting in python offline. I have gone through https://plot.ly/python/, but still I am not sure which will serve my purpose.

Please suggest something that will help me accomplish the above :)

Answer 1

This is the code to compute and visualize the spectrogram with plotly, i tested the code with this audio file: vignesh.wav The code was tested in Jupyter notebook using python 3.6

# Full example
import numpy as np
import matplotlib.pyplot as plt
# plotly offline
import plotly.offline as pyo
from plotly.offline import init_notebook_mode #to plot in jupyter notebook
import plotly.graph_objs as go
init_notebook_mode() # init plotly in jupyter notebook

from scipy.io import wavfile # scipy library to read wav files
AudioName = "vignesh.wav" # Audio File
fs, Audiodata = wavfile.read(AudioName)
Audiodata = Audiodata / (2.**15) # Normalized between [-1,1]

 #Spectrogram
from scipy import signal
plt.figure()
N = 512 #Number of point in the fft
w = signal.blackman(N)
freqs, bins, Pxx = signal.spectrogram(Audiodata, fs,window = w,nfft=N)

# Plot with plotly
trace = [go.Heatmap(
    x= bins,
    y= freqs,
    z= 10*np.log10(Pxx),
    colorscale='Jet',
    )]
layout = go.Layout(
    title = 'Spectrogram with plotly',
    yaxis = dict(title = 'Frequency'), # x-axis label
    xaxis = dict(title = 'Time'), # y-axis label
    )
fig = go.Figure(data=trace, layout=layout)
pyo.iplot(fig, filename='Spectrogram')