我正在写一个程序来识别来自麦克风的语音，代码将相应地进行处理。我为此编写的代码如下。

import speech_recognition as sr
import webbrowser
import pyttsx
from time import sleep

engine = pyttsx.init()
engine.setProperty('rate', 70)
r = sr.Recognizer()

def recognize(audio):
    try:
        return r.recognize(audio)
    except LookupError, e:
        print e
    return ''
with sr.Microphone() as source:
    while True:
        engine.say("Hi How can i help you ?")
        sleep(0.15)
        print "Start Speaking"
        audio = r.listen(source)
        words = recognize(audio)
        print("You said " + words)
        if words == "Facebook":
            engine.say("Shall i open the Facebook page for you ?")
            engine.runAndWait()
            audio = r.listen(source)
            words = recognize(audio)
            if words == "Yes":
                webbrowser.open('https://www.facebook.com')
        elif words == "stop":
            break

在这里，我也尝试了睡眠，但在引擎说话之前，我可以看到文本Start Speaking打印出来。除了睡眠，还有什么好的方法可以在麦克风中捕捉语音，然后等待说话或长时间沉默吗？