Sonification - sound of sand - 6

Frequency domain - What we did with volume in the previous post we now do with frequencies. The python program below converts the X- and Y-components of the shape into varying frequencies. The input shapes are the same as in the previous example. You can hear the sound samples here:

mp3 of small test shape

mp3 of big star shape

Again the sounds are very technical and abstract. I'll leave it like that for the moment. I'm still learning about what I can do. You can see the spectrum of the signal as it appears in Audacity:

 

It is easy to see that the spectrum now has the shape of the X- and Y- components of the shapes.

Next time I'll try to map the shape to the frequency domain while using the original waveform and not a pure sine signal. To do this I'll have to resample the waveform. This is a bit tricky to program but should give a more interesting signal.

In the meantime I've found a lot of interesting articles about shape sonification. In the future I'll try to do things with the curvature of the shape. And I haven't done anything with the spectral components yet.

from Nsound import *
import math

def convert_chaincode_to_x(c,x):
    if c == 1 or c == 0 or c == 7:
        x = x + 1
        return (x)
    elif ( c == 2 or c == 6):
        x = x
        return (x)
    else:
        x = x - 1
        return (x)

def convert_chaincode_to_y(c,y):
    if c == 1 or c == 2 or c == 3:
        y = y + 1
        return(y)
    elif c == 4 or c == 0:
        y = y
        return(y)
    else:
        y = y - 1
        return(y)

def sine_duration_frequency(duration, frequency):
    g = Generator(44100.0)
    length = math.ceil(float(duration) * float(frequency))/float(frequency)
    return g.drawSine(length, frequency)

def convert_xy_frequency(xy, minxy, maxxy, minf, maxf):
    r = float(maxf - minf)/float(maxxy - minxy)
    f = (xy - minxy)*r + minf
    return (f)

# ==============================

debug1  = False
debug2  = False
debug2a = False
debug3  = True

# read a chaincode .chc file that has been generated by SHAPE
infile = open("C:\\Users\\user\\Documents\\shape\\shape\\tiny_test.chc")
instr = infile.read()
infile.close()
if debug1:
    print instr

# parse the input file - split it into words
inwords = instr.split(' ')
if debug1:    print inwords

# delete anything except the chain code
i = 0
for str in inwords:
    if str.find('0E+0') > -1 :
        break
    i = i + 1
inwords = inwords[i+2:len(inwords)-1]
if debug1:
    print inwords

# fill the x and y buffer with the chaincode values
b_x_chaincode = Buffer()
b_y_chaincode = Buffer()

x = 0
y = 0
for str in inwords:
    c = int(str)
    x = convert_chaincode_to_x(c,x)
    b_x_chaincode << x
    y = convert_chaincode_to_y(c,y)
    b_y_chaincode << y

    if debug2a:
        print c
        print x

if debug2:
    b_x_chaincode.plot("x value from chaincode")
    Plotter.show()
    b_y_chaincode.plot("y value from chaincode")
    Plotter.show()

b_x_chaincode = b_x_chaincode - b_x_chaincode.getMean()
b_y_chaincode = b_y_chaincode - b_y_chaincode.getMean()

# generate a frequency modulated x and y signal
temp = Buffer()
b_x_long = Buffer()
b_y_long = Buffer()

soundpixel_length = 0.02
min_f = 40.0
max_f = 5000.0

min_x = b_x_chaincode.getMin()
max_x = b_x_chaincode.getMax()

if debug3:
    i=0

for x in b_x_chaincode:
    frequency = convert_xy_frequency(x, min_x, max_x, min_f, max_f)
    b_x_long << sine_duration_frequency(soundpixel_length, frequency)

    if debug3:
        i = i+1
        p = int(len(b_x_chaincode)/4)
        if i%p == 0:
            b = Buffer()
            b = sine_duration_frequency(soundpixel_length, frequency)
            b.plot(frequency)
            Plotter.show()

b_x_long.normalize()

min_y = b_y_chaincode.getMin()
max_y = b_y_chaincode.getMax()
for y in b_y_chaincode:
    frequency = convert_xy_frequency(y, min_y, max_y, min_f, max_f)
    b_y_long << sine_duration_frequency(soundpixel_length, frequency)
b_y_long.normalize()

# code the x and y signal into the left and right channel of an audio stream
# write the audio stream into a .wav file
a = AudioStream(44100.0, 2)
a[0] = b_x_long
a[1] = b_y_long
a.writeWavefile("C:\\Users\\user\\Documents\\shape\\shape\\tiny_test xy_freq_chaincode.wav")