# Template file for Homework 7, CS 151, Fall 2010, ISU # Name: (put your name here) # Collaborators: (put list of collaborators here, none if none). # ** Note on collaboration: You should not turn in work that is not your own. # To make sure you are not violating this, if you work with someone, # you should destroy the file once you are done working together, go # your separate ways, and then you should be able to recreate the file # on your own, then turn that in. If you cannot recreate the file on your # own, then it is not your work, and you should not turn it in. # ** Note on sources: if you use some other source, the web or whatever, you # better cite it! Not doing so is plagiarism. # Problem 1 (10 Points) # # This function is supposed to compute the number of times # the sound wave goes from negative to positive. # # If the function were correct, it would behave like this: # >>> sound = note(300, 1, 20000) # >>> negToPos = numNegToPos(sound) # Number of times wave goes from negative to positive is 299 # >>> sound = note(4, 1, 100) # Number of times wave goes from negative to positive is 3 # # You need to fill in the missing blanks _____ with what # should go there. After you do this, you should uncomment the # code to make sure it works! # #def numNegToPos(sound): # numNegToPos = 0 # lastValue = 0 # for i in range(0, getLength(sound)): # value = getSampleValueAt(_____, _____) # if (value >= 0 and lastValue < 0): # numNegToPos = _____ + 1 # lastValue = value # print "Number of times wave goes from negative to positive is", _____ # return numNegToPos # Problem 2 (10 Points) # # This function is supposed to compute the frequency of # a sound wave. # # If the function were correct, it would behave like this: # >>> sound = note(300, 1, 20000) # >>> freq = computeFrequency(sound) # Number of times wave goes from negative to positive is 299 # Frequency of the sound wave is about 299.0 # >>> sound = note(4, 1, 100) # >>> freq = computeFrequency(sound) # Number of times wave goes from negative to positive is 3 # Frequency of the sound wave is about 3.0 # # You need to fill in the missing blanks _____ with what # should go there. After you do this, you should uncomment the # code to make sure it works! # #def computeFrequency(sound): # negToPos = numNegToPos(_____) # samplingRate = getSamplingRate(_____) # numSamples = _____(sound) # seconds = float(numSamples)/samplingRate # freq = float(negToPos)/seconds # print "Frequency of the sound wave is about", _____ # return freq # Problem 3, Extra Credit (5 Points) # # Since this is extra credit, I will grade it a bit more strictly than # the regular problems. # # For this problem, you should make this function create # a new sound object that copies samples from the one that # is input. The new sound should be one with a reduced # sampling rate from the old one. This could be nice because # then the new sound will have fewer samples and will not # take up as many bytes. Of course, if the sampling rate is # made too small, the sound won't really sound like anything # anymore. # # You could call the function like this from the command window. # >>> sound = note(300, 1, 10000) # >>> play(sound) # >>> sound = reduceSamplingRate(sound, 2) # >>> play(sound) # And the sound will sound pretty much the same. You can # try it also on sound with people talking and see if it # sounds the same. def reduceSamplingRate(sound, factor): print "remove this and put your code here..." # The rest of this file has a few of the functions # we have done in class that you might like to use to # play around with sounds while working on this homework. # This is a function that will create a sound for # you that is a note of a given frequencey. You don't # have to understand it right now, but you can play around with it. # hertz is the frequency of the sound you want. # seconds is the number of seconds you want the sound to last. # sampleRate is the sampling rate of the sound file to be created. # You can call it like this in the command window. # >>> snd = note(261.626, 1, 22050) # >>> play(snd) def note(hertz, seconds, sampleRate): sound = makeEmptySoundBySeconds(seconds, sampleRate) samplesPerCycle = (sampleRate + 0.0)/hertz maxAmplitude = pow(2,15)-1 for i in range(0, seconds*sampleRate): t = i % samplesPerCycle scaledT = t * (2*pi/samplesPerCycle) value = sin(scaledT)*maxAmplitude setSampleValueAt(sound, i, value) return sound # normalizes a sound. def normalize(sound): largest = 0 for i in range(0, getLength(sound)): value = getSampleValueAt(sound, i) if (value > largest): largest = value # print "The largest value is", largest multiplier = (32767 + 0.0)/largest # print "Each sample value will be multiplied by", multiplier for i in range(0, getLength(sound)): value = getSampleValueAt(sound, i) setSampleValueAt(sound, i, value*multiplier) # blockingPlay(sound) # function to increase or decrease the volume of a sound. # sound sound be a sound that has been loaded with makeSound # multBy should be a number we want to multiply all the samples by. def changeVolume(sound, multBy): # for loop that will make s go over all the samples in the sound for s in getSamples(sound): # get the value of the sample in the sample object value = getSampleValue(s) # change the value of the sample in the sample object setSampleValue(s, value*multBy) # go ahead and play the new sound. use blockingPlay to make sure # we wait for any other sounds to finish before playing this one. # blockingPlay(sound) # function to change the volume only on the first half. # it uses getSampleValueAt and setSampleValueAt instead of # getSampleValue and setSampleValue to do this... def changeVolume1stHalf(sound, multBy): for i in range(0, getLength(sound)/2): # get the value of the i-th sample value = getSampleValueAt(sound, i) # change the value of the i-th sample setSampleValueAt(sound, i, value*multBy) # go ahead and play the new sound. use blockingPlay to make sure # we wait for any other sounds to finish before playing this one. # blockingPlay(sound)