Arduino问题：关于tone与IRremote冲突

void newtone(byte tonePin, int frequency, int duration) {
int period = 1000000L / frequency;
int pulse = period / 2;
for (long i = 0; i < duration *1000L; i += period) {
digitalWrite(tonePin, HIGH);
digitalWrite(led, HIGH);
delayMicroseconds(pulse);
digitalWrite(tonePin, LOW);
digitalWrite(led, LOW);
delayMicroseconds(pulse);

}
}
void start()
{
  for(int x=0;x<sizeof(Eulogyofjoytune)/sizeof(Eulogyofjoytune[0]);x++)
  {
    newtone(ALARM_PIN,Eulogyofjoytune[x],1);
  }
}

arduino处理tone函数和IRremote冲突问题时，建立了一个newtone函数
具体见：http://www.geek-workshop.com/thread-4037-1-1.html
但是不知道duration写啥，蜂鸣器一直响，无法产生不同频率的声音，请问这是为什么？