Increase volume by X decibels and rewrite audio file

Question

I'm new in naudio. And I wanna increase volume by X db. I've written this piece of code:

public static void IncreaseVolume(string inputPath, string outputPath, double db)
{            
    double linearScalingRatio = Math.Pow(10d, db / 10d);
    using (WaveFileReader reader = new WaveFileReader(inputPath))
    {
        VolumeWaveProvider16 volumeProvider = new VolumeWaveProvider16(reader);
        using (WaveFileWriter writer = new WaveFileWriter(outputPath, reader.WaveFormat))
        {
            while (true)
            {
                var frame = reader.ReadNextSampleFrame();
                if (frame == null)
                    break;
                writer.WriteSample(frame[0] * (float)linearScalingRatio);
            }
        }
    }
}

Ok, this works, but how can I find by how many decibels I've increased each sample? May anyone explain this moment for me and provide any examples?

UPDATE:

 using (WaveFileReader reader = new WaveFileReader(inFile))
            {
                float Sum = 0f;
                for (int i = 0; i < reader.SampleCount; i++)
                {
                    var sample = reader.ReadNextSampleFrame();
                    Sum += sample[0] * sample[0];
                }
                var db =  20 * Math.Log10(Math.Sqrt(Sum / reader.SampleCount) / 1);               
                Console.WriteLine(db);
                Console.ReadLine();
            }

Surely the decibel increase is dependent upon the volume of your output? Say you double the volume in the file, for some users that will be an increase of X db, for other users that will be an increase of Y db for a single frame, for a user who has muted, it will be an increase of 0 db, no matter what you do. — Lukazoid, Jun 05 '15 at 15:54
@Lukazoid wrong: As long as somthing arrives at the speaker, the (change in) dB value will be the same for all users/hardware — DrKoch, Jun 05 '15 at 16:17
Simply multiply the samples by Math.Pow(10.0, decibel / 20.0). Watch out for clipping. — Hans Passant, Jun 05 '15 at 17:45
Does this answer your question? [Calculate decibels](https://stackoverflow.com/questions/4152201/calculate-decibels) — JHBonarius, Aug 03 '22 at 08:01
Next time tag Naudio. The accepted answer is now very general, this not specific for naudio. Naudio has its own methods and adapters to the audio stream. — JHBonarius, Aug 03 '22 at 08:04

score 3 · Accepted Answer · answered Jun 05 '15 at 16:16

3

Your code looks good. To measure the average sound level of an audio sample you need to calculate the RMS (root mean square) of this sound level:

RMS := Sqrt( Sum(x_i*x_i)/N)

with x_i being the i-th sample and N the number of samples. The RMS is the average amplitude of your signal. Use

RMS_dB = 20*log(RMS/ref)

(with ref being 1.0 or 32767.0)

to convert it to a decibel value.

You may calculate this RMS value before and after you change the volume. The difference should be erxactly the dB you used in your IncreaseVolume()

answered Jun 05 '15 at 16:16

DrKoch

9,556
2
34
43

Try `double linearScalingRatio = Math.Pow(10d, db / 20.0);` in your code, then everything should be consistent. – DrKoch Jun 05 '15 at 20:34
This is nice theory, but the OP is using NAudio. NAudio provides its own interfaces. Do you have an NAudio specific answer? – JHBonarius Aug 03 '22 at 08:03

score 0 · Answer 2 · answered Aug 03 '22 at 06:09

0

Just adding a comment for people The input db in line is decibel and you need to convert it into amplitude. double linearScalingRatio = Math.Pow(10d, db / 10d);

The table is as follows- https://blog.demofox.org/2015/04/14/decibels-db-and-amplitude/

so you need to provide value as 6 in db, to make it twice as load. Another point already mentioned it should be double linearScalingRatio = Math.Pow(10d, db / 20d);

answered Aug 03 '22 at 06:09

Anant Kumar

1

This does not provide an answer to the question. Once you have sufficient [reputation](https://stackoverflow.com/help/whats-reputation) you will be able to [comment on any post](https://stackoverflow.com/help/privileges/comment); instead, [provide answers that don't require clarification from the asker](https://meta.stackexchange.com/questions/214173/why-do-i-need-50-reputation-to-comment-what-can-i-do-instead). - [From Review](/review/late-answers/32397243) – Hoppeduppeanut Aug 09 '22 at 04:33

Increase volume by X decibels and rewrite audio file

2 Answers2