IOS 通过麦克风检测声音分贝

来源：互联网发布：朗道知乎编辑：程序博客网时间：2024/05/16 01:01

在iphone真机上测的数据始始终没有变化，在模拟器上是可以的，折腾了半天，终于搜索找到解决方法，在代码中添加

[[AVAudioSession sharedInstance]        setCategory: AVAudioSessionCategoryPlayAndRecord error: nil];

1. 开发环境xocde5.1.1 ， IOS sdk7.1

2. 引入框架：AVFoundation.framework

3. 部分源码如下：

#import "MicBlowViewController.h"@implementation MicBlowViewController- (void)viewDidLoad{    [super viewDidLoad];         /* 必须添加这句话，否则在模拟器可以，在真机上获取始终是0  */    [[AVAudioSession sharedInstance]        setCategory: AVAudioSessionCategoryPlayAndRecord error: nil];    /* 不需要保存录音文件 */    NSURL *url = [NSURL fileURLWithPath:@"/dev/null"];        NSDictionary *settings = [NSDictionary dictionaryWithObjectsAndKeys:                [NSNumber numberWithFloat: 44100.0], AVSampleRateKey,                [NSNumber numberWithInt: kAudioFormatAppleLossless], AVFormatIDKey,                [NSNumber numberWithInt: 2], AVNumberOfChannelsKey,                [NSNumber numberWithInt: AVAudioQualityMax], AVEncoderAudioQualityKey,                nil];    NSError *error;    recorder = [[AVAudioRecorder alloc] initWithURL:url settings:settings error:&error];    if (recorder)    {        [recorder prepareToRecord];        recorder.meteringEnabled = YES;        [recorder record];        levelTimer = [NSTimer scheduledTimerWithTimeInterval: 1 target: self selector: @selector(levelTimerCallback:) userInfo: nil repeats: YES];    }    else    {        NSLog(@"%@", [error description]);    }    }/* 该方法确实会随环境音量变化而变化，但具体分贝值是否准确暂时没有研究 */- (void)levelTimerCallback:(NSTimer *)timer {[recorder updateMeters];     float   level;                // The linear 0.0 .. 1.0 value we need.    float   minDecibels = -80.0f; // Or use -60dB, which I measured in a silent room.    float   decibels    = [recorder averagePowerForChannel:0];        if (decibels < minDecibels)    {        level = 0.0f;    }    else if (decibels >= 0.0f)    {        level = 1.0f;    }    else    {        float   root            = 2.0f;        float   minAmp          = powf(10.0f, 0.05f * minDecibels);        float   inverseAmpRange = 1.0f / (1.0f - minAmp);        float   amp             = powf(10.0f, 0.05f * decibels);        float   adjAmp          = (amp - minAmp) * inverseAmpRange;                level = powf(adjAmp, 1.0f / root);    }        /* level 范围[0 ~ 1], 转为[0 ~120] 之间 */    dispatch_async(dispatch_get_main_queue(), ^{        [_textLabel setText:[NSString stringWithFormat:@"%f", level*120]];    });}- (void)dealloc {    [levelTimer release];    [recorder release];    [_textLabel release];    [_cLabel release];    [super dealloc];}@end

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