使用来自现场麦克风的pyaudio检测点击

Question

我将如何使用pyaudio来检测现场麦克风的突然敲击声？

Answer 1

我这样做的一种方式：

• 一次读取一块样本，比如说值得0.05秒
• 计算块的RMS幅度（各个样本的平方的平均值的平方根）
• 如果块的RMS幅度大于阈值，则为“嘈杂的块”，否则为“安静的块”
• 突然的敲击将是一个安静的区域，然后是少量的噪音区域，然后是一个安静的区域
• 如果您从不安静，则门槛太低
• 如果您从不听到嘈杂的声音，则您的门槛太高

我的应用程序正在录制无人看管的“有趣”噪音，因此只要有嘈杂的声音，它就会录制下来。如果有15秒的嘈杂时间（“遮住耳朵”），则将阈值乘以1.1；如果有15
分钟的 安静时间（“更难听”），则将阈值乘以0.9 。您的应用程序将有不同的需求。

此外，刚刚注意到我的代码中有关观察到的RMS值的一些注释。在Macbook Pro的内置麦克风上，标准化的音频数据范围为+/-
1.0，输入音量设置为max，一些数据点：

• 0.003-0.006（-50dB至-44dB）我家的中央暖气风扇
• 在同一台笔记本电脑上键入0.010-0.40（-40dB至-8dB）
• 0.10（-20dB）在1’距离处轻柔地弹指
• 0.60（-4.4dB）在1’处大声响动

更新：这是一个入门的示例。

#!/usr/bin/python

# open a microphone in pyAudio and listen for taps

import pyaudio
import struct
import math

INITIAL_TAP_THRESHOLD = 0.010
FORMAT = pyaudio.paInt16 
SHORT_NORMALIZE = (1.0/32768.0)
CHANNELS = 2
RATE = 44100  
INPUT_BLOCK_TIME = 0.05
INPUT_FRAMES_PER_BLOCK = int(RATE*INPUT_BLOCK_TIME)
# if we get this many noisy blocks in a row, increase the threshold
OVERSENSITIVE = 15.0/INPUT_BLOCK_TIME                    
# if we get this many quiet blocks in a row, decrease the threshold
UNDERSENSITIVE = 120.0/INPUT_BLOCK_TIME 
# if the noise was longer than this many blocks, it's not a 'tap'
MAX_TAP_BLOCKS = 0.15/INPUT_BLOCK_TIME

def get_rms( block ):
    # RMS amplitude is defined as the square root of the 
    # mean over time of the square of the amplitude.
    # so we need to convert this string of bytes into 
    # a string of 16-bit samples...

    # we will get one short out for each 
    # two chars in the string.
    count = len(block)/2
    format = "%dh"%(count)
    shorts = struct.unpack( format, block )

    # iterate over the block.
    sum_squares = 0.0
    for sample in shorts:
        # sample is a signed short in +/- 32768. 
        # normalize it to 1.0
        n = sample * SHORT_NORMALIZE
        sum_squares += n*n

    return math.sqrt( sum_squares / count )

class TapTester(object):
    def __init__(self):
        self.pa = pyaudio.PyAudio()
        self.stream = self.open_mic_stream()
        self.tap_threshold = INITIAL_TAP_THRESHOLD
        self.noisycount = MAX_TAP_BLOCKS+1 
        self.quietcount = 0 
        self.errorcount = 0

    def stop(self):
        self.stream.close()

    def find_input_device(self):
        device_index = None            
        for i in range( self.pa.get_device_count() ):     
            devinfo = self.pa.get_device_info_by_index(i)   
            print( "Device %d: %s"%(i,devinfo["name"]) )

            for keyword in ["mic","input"]:
                if keyword in devinfo["name"].lower():
                    print( "Found an input: device %d - %s"%(i,devinfo["name"]) )
                    device_index = i
                    return device_index

        if device_index == None:
            print( "No preferred input found; using default input device." )

        return device_index

    def open_mic_stream( self ):
        device_index = self.find_input_device()

        stream = self.pa.open(   format = FORMAT,
                                 channels = CHANNELS,
                                 rate = RATE,
                                 input = True,
                                 input_device_index = device_index,
                                 frames_per_buffer = INPUT_FRAMES_PER_BLOCK)

        return stream

    def tapDetected(self):
        print("Tap!")

    def listen(self):
        try:
            block = self.stream.read(INPUT_FRAMES_PER_BLOCK)
        except IOError as e:
            # dammit. 
            self.errorcount += 1
            print( "(%d) Error recording: %s"%(self.errorcount,e) )
            self.noisycount = 1
            return

        amplitude = get_rms( block )
        if amplitude > self.tap_threshold:
            # noisy block
            self.quietcount = 0
            self.noisycount += 1
            if self.noisycount > OVERSENSITIVE:
                # turn down the sensitivity
                self.tap_threshold *= 1.1
        else:            
            # quiet block.

            if 1 <= self.noisycount <= MAX_TAP_BLOCKS:
                self.tapDetected()
            self.noisycount = 0
            self.quietcount += 1
            if self.quietcount > UNDERSENSITIVE:
                # turn up the sensitivity
                self.tap_threshold *= 0.9

if __name__ == "__main__":
    tt = TapTester()

    for i in range(1000):
        tt.listen()