EAS header .wav audio generator

# (Amplitude bug has been fixed)
# (Severe LSB bug has been fixed...)
# This program generates a classic digital EAS (SAME) header, with preamble followed by message data
# According to standard, the header is repeated 3 times, including preamble, with 1 second inbetween.
# It then saves the signal to an uncompressed .wav file with the given file name
# The bits are encoded as 4 sine wave cycles for a 1 and 3 cycles for a 0, over a standard timespan of 1.92ms
# Each character (ASCII standard) is transmitted least significant bit first
# This program allows you to generate any header you want, but for valid headers, the format can be found at:
# https://en.wikipedia.org/wiki/Specific_Area_Message_Encoding

from math import sin, pi
import wave

# Freely modifiable variables:
message = "Example message, type anything you want! (as long as it's ASCII)"
filename = 'signalaudio.wav'
rate = 44100 # sample rate in hz
bitlength = 0.00192 # bit length in seconds, recommend not changing
amplitude = 1.0 # range between 0 and 1
# ----------

sample_width = 1
max_amplitude = 2 ** (8 * sample_width) - 1
half_max_amp = 0.5 * max_amplitude
wav = wave.open(filename, 'wb')
wav.setnchannels(1)
wav.setsampwidth(sample_width)
wav.setframerate(rate)

def bits_lsb(_bytes):
    for byte in _bytes:
        for i in range(8):
            yield (byte >> i) & 1

def generate_bit_signal(ncycles):
    cycle = bytearray()
    samples_per_cycle = round(rate * bitlength / ncycles)
    for i in range(samples_per_cycle):
        cycle.append(round(amplitude * half_max_amp * sin(i * 2 * pi / samples_per_cycle) + half_max_amp))
    return bytes(cycle * ncycles)

MARK = generate_bit_signal(4)
SPACE = generate_bit_signal(3)

def generate_byte_signal(_bytes):
    signal = bytearray()
    for bit in bits_lsb(_bytes):
        signal.extend(MARK if bit == 1 else SPACE)
    return bytes(signal)

data = (generate_byte_signal(b'\xAB' * 16 + bytes(message, encoding='ascii')) + bytes([int(half_max_amp)]) * rate) * 3

wav.writeframes(data)
wav.close()