[英]What do I measure with pyAudio?
我正在使用python pyAudio库录制声音,并使用matplotlib进行绘制。 在这里,我正在记录音量,并想知道该音量是多少,这是多少个Dezibel。
目前,我认为它已记录在PCM中 ,但我不确定。
在这一部分中,我将按照docs中的说明设置流:
# 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
)
这是我测量音频信号的部分:
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]
这是整个代码:
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轴上的值为255,我想知道它的单位并将其转换为Dezibel。
Y轴单位是绝对音量水平。 如果要转换为分贝dB,则等式为
Volume(dB) = 20*log10(v1/v0)
,其中v0是基准参考电平。
以下网址具有许多与声音,放大等有关的有用概念。
http://www.sengpielaudio.com/calculator-soundvalues.htm上面有一个表格,该表格将dB与声音水平相关。
http://www.sengpielaudio.com/calculator-FactorRatioLevelDecibel.htm
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