[英]What do I measure with pyAudio?
我正在使用python pyAudio庫錄制聲音,並使用matplotlib進行繪制。 在這里,我正在記錄音量,並想知道該音量是多少,這是多少個Dezibel。
目前,我認為它已記錄在PCM中 ,但我不確定。
在這一部分中,我將按照docs中的說明設置流:
# constants
CHUNK = 1024 * 2 # samples per frame
FORMAT = pyaudio.paInt16 # audio format (bytes per sample?)
CHANNELS = 1 # single channel for microphone
RATE = 44100 # samples per second
# pyaudio class instance
mic = pyaudio.PyAudio()
# stream object to get data from microphone
stream = mic.open(
format=FORMAT,
channels=CHANNELS,
rate=RATE,
input=True,
output=True,
frames_per_buffer=CHUNK
)
這是我測量音頻信號的部分:
def measure():
# binary data
data = stream.read(CHUNK)
# convert data to integers, make np array, then offset it by 127
data_int = struct.unpack(str(2 * CHUNK) + 'B', data)
# create np array and offset by 128
data_np = np.array(data_int, dtype='b')[::2]
data_np = [i+127 for i in data_np]
這是整個代碼:
import pyaudio #for capturing the audio-signal
import struct #for converting the binary-data from the signal to integer
import matplotlib.pyplot as plt #for displaying the audio-signal
import numpy as np
import time
#functions
def plot_setup():
# create matplotlib figure and axes
fig=plt.figure()
ax=fig.add_subplot(111)
# variable for plotting
x = np.arange(0, 2 * CHUNK, 2)
# create a line object with random data
line, = ax.plot(x, [128 for i in range(2048)], '-')
# basic formatting for the axes
ax.set_title('AUDIO WAVEFORM')
ax.set_xlabel('samples')
ax.set_ylabel('volume')
ax.set_ylim(0, 255)
ax.set_xlim(0, 2 * CHUNK)
plt.xticks([0, CHUNK, 2 * CHUNK])
plt.yticks([0, 128, 255])
# show the plot
plt.show(block=False)
return fig, line
def measure():
# binary data
data = stream.read(CHUNK)
# convert data to integers, make np array, then offset it by 127
data_int = struct.unpack(str(2 * CHUNK) + 'B', data)
# create np array and offset by 128
data_np = np.array(data_int, dtype='b')[::2]
data_np = [i+127 for i in data_np]
line.set_ydata(data_np)
try:
fig.canvas.draw()
fig.canvas.flush_events()
except:
return 0
# constants
CHUNK = 1024 * 2 # samples per frame
FORMAT = pyaudio.paInt16 # audio format (bytes per sample?)
CHANNELS = 1 # single channel for microphone
RATE = 44100 # samples per second
# pyaudio class instance
mic = pyaudio.PyAudio()
# stream object to get data from microphone
stream = mic.open(
format=FORMAT,
channels=CHANNELS,
rate=RATE,
input=True,
output=True,
frames_per_buffer=CHUNK
)
if __name__=="__main__":
fig, line=plot_setup()
while True:
m=measure()
if m==0:
break
y軸上的值為255,我想知道它的單位並將其轉換為Dezibel。
Y軸單位是絕對音量水平。 如果要轉換為分貝dB,則等式為
Volume(dB) = 20*log10(v1/v0)
,其中v0是基准參考電平。
以下網址具有許多與聲音,放大等有關的有用概念。
http://www.sengpielaudio.com/calculator-soundvalues.htm上面有一個表格,該表格將dB與聲音水平相關。
http://www.sengpielaudio.com/calculator-FactorRatioLevelDecibel.htm
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