7. Audio: SoundEffects V2

7.1. Sound Effect Syntax

class audio.SoundEffect(freq_start=500, freq_end=2500, duration=500, vol_start=255, vol_end=0, waveform=audio.SoundEffect.WAVEFORM_SQUARE, fx=audio.SoundEffect.FX_NONE, shape=audio.SoundEffect.SHAPE_LOG)

audio.SoundEffect() represents a sound effect that can be played.

Parameters:

  • freq_start – Start frequency in Hertz (Hz), range 0-9999, default: 500

  • freq_end – End frequency in Hertz (Hz), , range 0-9999, default: 2500

  • duration – Duration of the sound (ms), , range 0-9999, default: 500

  • vol_start – Start volume value, range 0-255, default: 255

  • vol_end – End volume value, range 0-255, default: 0

  • waveform – Type of waveform shape, one of these values: audio.SoundEffect.WAVEFORM_SINE, audio.SoundEffect.WAVEFORM_SAWTOOTH, audio.SoundEffect.WAVEFORM_TRIANGLE, audio.SoundEffect.WAVEFORM_SQUARE, audio.SoundEffect.WAVEFORM_NOISE (randomly generated noise). Default: WAVEFORM_SQUARE

  • fx – Effect to add on the sound, one of the following values: audio.SoundEffect.FX_TREMOLO, audio.SoundEffect.FX_VIBRATO, audio.SoundEffect.FX_WARBLE, or audio.SoundEffect.FX_NONE. Default: audio.SoundEffect.FX_NONE

  • shape – The type of the interpolation curve between the start and end frequencies, different wave shapes have different rates of change in frequency. One of the following values: audio.SoundEffect.SHAPE_LINEAR, audio.SoundEffect.SHAPE_CURVE, audio.SoundEffect.SHAPE_LOG. Default: audio.SoundEffect.SHAPE_LOG

The parameter values can all be modified via attributes of the same name.
For example, first create an effect my_effect = SoundEffect(duration=1000),

then change its attribute for duration: my_effect.duration = 500.

7.2. Vary frequencies

The code below plays different sound effects by pressing the A or B button on the microbit.
The sound effect’s frequency sweep goes from low to high when the A button is pressed, and from high to low when the B button is pressed.
When the A button is pressed, the start frequency is increased in steps while the end frequency is kept the same.
from microbit import *
import audio

sound_effect = audio.SoundEffect()  # use defaults
while True:
    if button_a.is_pressed():
        sound_effect.freq_start = 880 - (100 * 4)
        sound_effect.freq_end = 880
        for freq_step in range(4):
            sound_effect.freq_start += 100
            audio.play(sound_effect, wait=True)
            sleep(100)
    sleep(50)

Tasks

  1. Modify the code above to so that when the B button is pressed, the start frequency is kept the same while the end frequency is increased in steps.

  2. Use both the A and B-button pressing code and replace all values with variables: base_freq, step_size, steps.

  3. Modify the code above to use definitions with parameters. Name the def block, increase_freq, for A-buuton pressing and decrease_freq, for B-buuton pressing.

Modify the code above to so that when the B button is pressed, the start frequency is kept the same while the end frequency is increased in steps.

from microbit import *
import audio

sound_effect = audio.SoundEffect()  # use defaults
base_freq = 880
step_size = 100
steps = 4
while True:
    if button_b.is_pressed():
        sound_effect.freq_start = 880
        sound_effect.freq_end = 880 - (100 * 4)
        for freq_step in range(4):
            audio.play(sound_effect, wait=True)
            sound_effect.freq_end += 100
            sleep(100)
    sleep(50)

Use both the A and B-button pressing code and replace all values with variables: base_freq, step_size, steps.

from microbit import *
import audio

sound_effect = audio.SoundEffect()  # use defaults
base_freq = 880
step_size = 100
steps = 4
while True:
    if button_a.is_pressed():
        sound_effect.freq_start = base_freq - (step_size * steps)
        sound_effect.freq_end = base_freq
        for freq_step in range(steps):
            audio.play(sound_effect, wait=True)
            sound_effect.freq_start += step_size
            sleep(100)
    elif button_b.is_pressed():
        sound_effect.freq_start = base_freq
        sound_effect.freq_end = base_freq - (step_size * steps)
        for freq_step in range(steps):
            audio.play(sound_effect, wait=True)
            sound_effect.freq_end += step_size
            sleep(100)
    sleep(50)

Modify the code above to use definitions with parameters. Name the def block, increase_freq, for A-buuton pressing and decrease_freq, for B-buuton pressing.

from microbit import *
import audio


def increase_freq(sound_effect, base_freq, step_size, steps):
    sound_effect.freq_start = base_freq - (step_size * steps)
    sound_effect.freq_end = base_freq
    for freq_step in range(steps):
        audio.play(sound_effect, wait=True)
        sound_effect.freq_start += step_size
        sleep(100)

def decrease_freq(sound_effect, base_freq, step_size, steps):
    sound_effect.freq_start = base_freq
    sound_effect.freq_end = base_freq - (step_size * steps)
    for freq_step in range(steps):
        audio.play(sound_effect, wait=True)
        sound_effect.freq_end += step_size
        sleep(100)

sound_effect = audio.SoundEffect()  # use defaults
base_freq = 880
step_size = 100
steps = 4

while True:
    if button_a.is_pressed():
        increase_freq(sound_effect, base_freq, step_size, steps)
    elif button_b.is_pressed():
        decrease_freq(sound_effect, base_freq, step_size, steps)
    sleep(50)

7.3. Vary the waveform

The code below plays sounds based on the default sound effect.
When the A button is pressed, each of the different waveforms is tried.
Which waveforms sound similar?
from microbit import *
import audio

sound_effect = audio.SoundEffect()  # use defaults
waveform_list = [audio.SoundEffect.WAVEFORM_SINE, audio.SoundEffect.WAVEFORM_SAWTOOTH,
                 audio.SoundEffect.WAVEFORM_TRIANGLE, audio.SoundEffect.WAVEFORM_SQUARE,
                 audio.SoundEffect.WAVEFORM_NOISE]

while True:
    if button_a.is_pressed():
        for waveform_choice in waveform_list:
            sound_effect.waveform = waveform_choice
            audio.play(sound_effect, wait=True)
            sleep(500)
    sleep(50)

7.4. microbit scale function

scale(value, from_, to)

Converts a value from a range to another range.

Parameters:

  • value – A number to convert.

  • from – A tuple to define the range to convert from.

  • to – A tuple to define the range to convert to.

Returns:

The value (float or int; int returned if both to vlaeus are integers) converted to the to range.

e.g. scaled_value = scale(200, from_=(0,255), to=(0, 10))

Tasks

  1. Modify the code above to use the x-tilt of the microbit to choose the waveform to use from the list. Use the scale function to scale the x accelerometer readings to integers form 0 to 4.

Modify the code above use the x-tilt of the microbit to choose the waveform to use from the list. Use the scale function to scale the x accelerometer readings to integers form 0 to 4.

from microbit import *
import audio

sound_effect = audio.SoundEffect()  # use defaults
waveform_list = [audio.SoundEffect.WAVEFORM_SINE, audio.SoundEffect.WAVEFORM_SAWTOOTH,
                audio.SoundEffect.WAVEFORM_TRIANGLE, audio.SoundEffect.WAVEFORM_SQUARE,
                audio.SoundEffect.WAVEFORM_NOISE]

while True:
    if button_a.is_pressed():
        xreading = abs(accelerometer.get_x())
        waveform_index = scale(accelerometer.get_x(), from_=(-1023, 1023), to=(0, 4))
        sound_effect.waveform = waveform_list[waveform_index]
        audio.play(sound_effect, wait=True)
        sleep(500)
    sleep(50)

7.5. Vary the fx

The code below plays sounds based on the default sound effect.
When the A button is pressed, each of the different add on effects is tried.
from microbit import *
import audio

sound_effect = audio.SoundEffect()  # use defaults
fx_list =[audio.SoundEffect.FX_TREMOLO, audio.SoundEffect.FX_VIBRATO,
            audio.SoundEffect.FX_WARBLE, audio.SoundEffect.FX_NONE]

while True:
    if button_a.is_pressed():
        for fx_choice in fx_list:
            sound_effect.fx = fx_choice
            audio.play(sound_effect, wait=True)
            sleep(500)
    sleep(50)

7.6. Copying sound effects

Copying a sound effects can be useful when a second sound effect is to be based on another.
copy()
Returns:

A copy of the SoundEffect.

The code below specifies a sound effect, snd_effect1, start and end frequencies.
snd_effect1 si copied to snd_effect2, which is then modified.
A and B-buttons are used to play the 2 sound effects.
from microbit import *
import audio

# Create a new Sound Effect and immediately play it
snd_effect1 = audio.SoundEffect(freq_start=300, freq_end=1200)

snd_effect2 = snd_effect1.copy()
snd_effect2.freq_start = 2100
snd_effect2.waveform=audio.SoundEffect.WAVEFORM_SAWTOOTH

while True:
    if button_a.is_pressed():
        # the A-button silences the microbit
        audio.play(snd_effect1, wait=False)
        sleep(500)
    elif button_b.is_pressed():
        # B-button re-enables the speaker & plays an effect while showing an image
        audio.play(snd_effect2, wait=False)
        sleep(500)
    sleep(50)

Tasks

  1. Modify the code above to use the laser sound effect and a copy at double the frequency: laser = audio.SoundEffect(freq_start=1600, freq_end=400, duration=400, shape=audio.SoundEffect.SHAPE_CURVE)

  1. Modify the code above to use the laser sound effect and a copy at double the frequency: laser = audio.SoundEffect(freq_start=1600, freq_end=400, duration=400, shape=audio.SoundEffect.SHAPE_CURVE)

from microbit import *
import audio

# Create a new Sound Effect and immediately play it
laser = audio.SoundEffect(freq_start=1600, freq_end=400, duration=400,
                        shape=audio.SoundEffect.SHAPE_CURVE)

laser2 = laser.copy()
laser2.freq_start = 3200
laser2.freq_end=800

while True:
    if button_a.is_pressed():
        # the A-button silences the microbit
        audio.play(laser, wait=False)
        sleep(500)
    elif button_b.is_pressed():
        # B-button re-enables the speaker & plays an effect while showing an image
        audio.play(laser2, wait=False)
        sleep(500)
    sleep(50)

7.7. Custom sound effects

The code below plays the custom sound effects when the A-button is pressed.
from microbit import *
import audio


laser = audio.SoundEffect(freq_start=1600, freq_end=400, duration=1000,
                        shape=audio.SoundEffect.SHAPE_CURVE)

radio_snd = audio.SoundEffect(freq_start=500, freq_end=499, duration=1000,
                        waveform=audio.SoundEffect.WAVEFORM_NOISE,
                        shape=audio.SoundEffect.SHAPE_LINEAR)

jump = audio.SoundEffect(freq_start=400, freq_end=600, duration=1000,
                        shape=audio.SoundEffect.SHAPE_LINEAR)

snare = audio.SoundEffect(freq_start=523, freq_end=1, duration=1000,
                        waveform=audio.SoundEffect.WAVEFORM_NOISE)

sound_names = [laser, radio_snd, jump, snare]

while True:
    if button_a.is_pressed():
        for snd in sound_names:
            audio.play(snd, wait=True)
            sleep(500)
    sleep(50)

Exercise

  1. Play 2 of the sound effects on A-button pressing and another two on B-button pressing.

7.8. Transferring Sound Effects

The repr() function can be used to create a string of Python code that can be sent by radio.
SoundEffect(500, 2500, 500, 255, 0, 3, 0, 18)
This code below allows two or more microbits to send and receive sound effects to each other over radio.
When a user presses the A-button, it sends the predefined sound effects to all other microbits in the same radio group.
When a microbit receives a sound effect, it plays the sound effect.
The sound effects are represented as strings of parameters that are sent over the radio and then converted back into sound effects on the receiving microbit.
snd_eff_str = repr(snd_var): This line is using the built-in Python function repr() to create a string representation of the snd_var object, which is an instance of the SoundEffect class. The repr() function returns a string that would yield an object with the same value when passed to eval(). In this case, it returns a string that looks like a valid Python expression, which could be used to recreate an object with the same value.
start = snd_eff_str.find("(") + 1: This line is finding the position of the first opening parenthesis “(” in the snd_eff_str string, and adding 1 to it. This is done to get the start index for slicing the string to extract the parameters of the SoundEffect.
end = snd_eff_str.find(")"): This line is finding the position of the first closing parenthesis “)” in the snd_eff_str string. This is the end index for slicing the string.
params = snd_eff_str[start:end]: This line is slicing the snd_eff_str string from start to end to get the parameters of the SoundEffect. The result is a string of numbers separated by commas, which represent the parameters of the SoundEffect.
mparams = tuple(map(int, incoming_message.split(','))): This line is splitting the incoming_message string at each comma and converting each resulting string to an integer. The results are then packed into a tuple and assigned to mparams.
sound_effect = audio.SoundEffect(*mparams): This line is creating a SoundEffect object from the audio module. The *mparams syntax is using tuple unpacking to pass the values in mparams as arguments to SoundEffect.
In summary, these lines of code are converting a SoundEffect object to a string representation, and then extracting the parameters of the SoundEffect from the string. This allows the parameters to be sent over the radio as a string, and then converted back into a SoundEffect on the receiving microbit.
from microbit import *
import radio
import audio

# Choose own group in pairs 0-255
radio.config(group=8, length=251)
# Turn on the radio
radio.on()

'''
default sound effect
audio.SoundEffect(freq_start=500, freq_end=2500, duration=500,
vol_start=255, vol_end=0,
waveform=audio.SoundEffect.WAVEFORM_SQUARE,
fx=audio.SoundEffect.FX_NONE,
shape=audio.SoundEffect.SHAPE_LOG)
'''

laser = audio.SoundEffect(freq_start=1600, freq_end=400, duration=1000,
                        shape=audio.SoundEffect.SHAPE_CURVE)

radio_snd = audio.SoundEffect(freq_start=500, freq_end=499, duration=1000,
                        waveform=audio.SoundEffect.WAVEFORM_NOISE,
                        shape=audio.SoundEffect.SHAPE_LINEAR)

jump = audio.SoundEffect(freq_start=400, freq_end=600, duration=1000,
                        shape=audio.SoundEffect.SHAPE_LINEAR)

snare = audio.SoundEffect(freq_start=523, freq_end=1, duration=1000,
                        waveform=audio.SoundEffect.WAVEFORM_NOISE)

sound_names = [laser, radio_snd, jump, snare]


while True:
    # send
    if button_a.was_pressed():
        counter = 0
        for snd_var in sound_names:
            counter += 1
            radio.send(str(counter))
            snd_eff_str = repr(snd_var)
            # "SoundEffect(54, 54, 1000, 255, 0, 4, 0, 1)"
            start = snd_eff_str.find("(") + 1
            end = snd_eff_str.find(")")
            params = snd_eff_str[start:end]
            # "54, 54, 1000, 255, 0, 4, 0, 1"
            radio.send(params)

    # receive
    incoming_message = radio.receive()
    if incoming_message is not None:
        if len(incoming_message) < 5:
            display.show(incoming_message)
        else:
            # Convert the message back to a tuple of integers: 54, 54, 1000, 255, 0, 4, 0, 1)
            mparams = tuple(map(int, incoming_message.split(',')))
            # Create the sound effect with tuple unpacking: audio.SoundEffect(54, 54, 1000, 255, 0, 4, 0, 1)
            sound_effect = audio.SoundEffect(*mparams)
            # Play the sound effect
            audio.play(sound_effect)
            sleep(600)

Exercise

  1. Use A and B-buttons to send diffferent custom sound effects to another microbit.