打开扬声器：

[[AVAudioSession sharedInstance] overrideOutputAudioPort:AVAudioSessionPortOverrideSpeaker error:nil];

关闭扬声器：

[[AVAudioSession sharedInstance] overrideOutputAudioPort:AVAudioSessionPortOverrideNone error:nil];

注意：

1:iPad不需要打开关闭扬声器：因为iPad只有扬声器

2:在打开和关闭养生起的时候，需要对耳机做处理，如果当前处于耳机插入的时候，打开扬声器是没有作用的。所以需要监听当前音频轨道变化。
//添加耳机拔掉侦听事件

AudioSessionInitialize(NULL, NULL, NULL, NULL);

       AudioSessionAddPropertyListener(kAudioSessionProperty_AudioRouteChange,        audioRouteChangeCallback, (__bridge void *)(self));

//耳机拔掉侦听事件回调 [AudioManager 为当前类，即为self]

 void audioRouteChangeCallback(void*inClientData,AudioSessionPropertyIDinID, UInt32inDataSize,constvoid*inData)
{
    CFDictionaryRefrouteChangeDictionary = inData;
    CFNumberRefrouteChangeReasonRef =CFDictionaryGetValue(routeChangeDictionary,CFSTR(kAudioSession_AudioRouteChangeKey_Reason));
    SInt32routeChangeReason;
CFNumberGetValue(routeChangeReasonRef,kCFNumberSInt32Type, &routeChangeReason);
    AudioManager*_self = (__bridgeAudioManager*)inClientData;
    if (routeChangeReason == kAudioSessionRouteChangeReason_OldDeviceUnavailable) {    //拔掉耳机
        [_self setSpeakerOn];
    }else if (routeChangeReason ==kAudioSessionRouteChangeReason_NewDeviceAvailable) {    //插入耳机
    }
}

//检测当前是否有耳机：

- (BOOL)hasHeadset
{
    CFStringRef route;
    UInt32propertySize =sizeof(CFStringRef);
    AudioSessionGetProperty(kAudioSessionProperty_AudioRoute, &propertySize, &route);
    if((route ==NULL) || (CFStringGetLength(route) ==0))
    {
        // Silent Mode
    }
    else
    {
        NSString* routeStr = (__bridge_transferNSString*)route;
        NSRangeheadphoneRange = [routeStrrangeOfString:@"Headphone"];
        NSRangeheadsetRange = [routeStrrangeOfString:@"Headset"];
        if(headphoneRange.location!=NSNotFound)
        {
            returnYES;
        }elseif(headsetRange.location!=NSNotFound)
        {
            returnYES;
        }
    }
    return NO;
}