函数名: nosound 
 功  能: 关闭PC扬声器 
 用  法: #include <dos.h>
         void nosound(void); 
 程序例: 
/* Emits a 7-Hz tone for 10 seconds.
     True story: 7 Hz is the resonant frequency of a chicken's skull cavity. 
      This was determined empirically in Australia, where a new factory 
      generating 7-Hz tones was located too close to a chicken ranch: 
      When the factory started up, all the chickens died. 
Your PC may not be able to emit a 7-Hz tone. 
 */ 
#include <dos.h>
int main(void) 
 { 
    sound(7); 
    delay(10000); 
    nosound(); 
 }