Android如何查找分贝 [英] Android How To Find Decibels

问题描述

我正试图从麦克风上获得分贝，并且到处都在寻找如何正确执行分贝的方法，但是它们似乎没有用.

I'm trying to get the decibels from the microphone and have looked everywhere how to correctly do it but they don't seem to work.

我得到这样的振幅

public class SoundMeter {
static final private double EMA_FILTER = 0.6;

private MediaRecorder mRecorder = null;
private double mEMA = 0.0;

public void start()  {
    if (mRecorder == null) {
        mRecorder = new MediaRecorder();
        mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
        mRecorder.setOutputFile("/dev/null/");

        try {
            mRecorder.prepare();
        } catch (IllegalStateException | IOException e) {
            e.printStackTrace();
        }
        mRecorder.start();
        mEMA = 0.0;
    }
}

public void stop() {
    if (mRecorder != null) {
        mRecorder.stop();
        mRecorder.release();
        mRecorder = null;
    }
}

public double getTheAmplitude(){
    if(mRecorder != null)
        return (mRecorder.getMaxAmplitude());
    else
        return 1;
}
public double getAmplitude() {
    if (mRecorder != null)
        return  (mRecorder.getMaxAmplitude()/2700.0);
    else
        return 0;

}

public double getAmplitudeEMA() {
    double amp = getAmplitude();
    mEMA = EMA_FILTER * amp + (1.0 - EMA_FILTER) * mEMA;
    return mEMA;
}

}

然后在我的其他活动中，我调用getAmplitude方法，它返回振幅.要将其转换为分贝，我使用以下方法:

Then In my other activity I call the getAmplitude method an it returns the amplitude.To convert it to decibels I use this:

dB =  20 * Math.log10(soundMeter.getAmplitude() / 32767);

我已经为32767尝试了许多不同的值，但似乎没有一个给我一个现实的分贝答案.通常是负数，有时是无穷大.如果您知道如何正确找到分贝，请提供帮助.

Ive tried many different values in place for the 32767 but none of them seem to give me a realistic decibel answer. It's usually negative and sometimes -infinity. Please help if you know how to find decibels the right way.

推荐答案

getMaxAmplitude返回0到32767之间的数字.要将其转换为dB，您需要首先将其缩放为0到-1之间的值. 20 * log10(1)== 0 和 20 * log10(0)==-inf .

getMaxAmplitude returns a number between 0 and 32767. To convert that to dB you need to first scale it to to a value between 0 and -1. 20*log10(1)==0 and 20*log10(0)==-inf.

如果获取-inf，则只能是因为要将0传递给log函数.这很可能是因为您要进行整数除法.将分母更改为双精度以强制进行浮点除法.

If you're getting -inf then this can only be because you're passing 0 to the log function. This is most likely because you are doing integer division. Change the denominator to a double to force a floating point division.

double dB = 20*log10(x / 32767.0);

这篇关于Android如何查找分贝的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！