callnotifier.java
public void run() {
......
switch (mToneId) {
case TONE_CALL_WAITING:
toneType = ToneGenerator.TONE_SUP_CALL_WAITING;
toneVolume = TONE_RELATIVE_VOLUME_HIPRI; //可以更改这个音量，目前是80，代表相对其它声音的大小
// Call waiting tone is stopped by stopTone() method
toneLengthMillis = Integer.MAX_VALUE - TONE_TIMEOUT_BUFFER;
break;android通话时第二通电话呼叫等待提示音音量大小
原文：http://blog.csdn.net/sergeycao/article/details/40581037
