前言
wav音频添加自定义时长静音的工具类

Maven依赖
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>30.1.1-jre</version>
        </dependency>
        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>5.5.2</version>
        </dependency>
代码
package ai.guiji.csdn.tools;

import cn.hutool.core.io.FileUtil;
import cn.hutool.core.io.IoUtil;
import cn.hutool.core.util.IdUtil;
import cn.hutool.core.util.URLUtil;
import com.google.common.base.Joiner;
import com.google.common.primitives.Bytes;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.LongStream;

/** java项目 fhadmin.cn **/
public class WavAddSilenceUtils {
  /**
   * 根据PCM文件构建wav的header字段
   *
   * @param srate Sample rate - 8000, 16000, etc.
   * @param channel Number of channels - Mono = 1, Stereo = 2, etc..
   * @param format Number of bits per sample (16 here)
   * @throws IOException
   */
  public static byte[] buildWavHeader(int dataLength, int srate, int channel, int format)
      throws IOException {
    byte[] header = new byte[44];

    long totalDataLen = dataLength + 36;
    long bitrate = srate * channel * format;

    header[0] = 'R';
    header[1] = 'I';
    header[2] = 'F';
    header[3] = 'F';
    header[4] = (byte) (totalDataLen & 0xff);
    header[5] = (byte) ((totalDataLen >> 8) & 0xff);
    header[6] = (byte) ((totalDataLen >> 16) & 0xff);
    header[7] = (byte) ((totalDataLen >> 24) & 0xff);
    header[8] = 'W';
    header[9] = 'A';
    header[10] = 'V';
    header[11] = 'E';
    header[12] = 'f';
    header[13] = 'm';
    header[14] = 't';
    header[15] = ' ';
    header[16] = (byte) format;
    header[17] = 0;
    header[18] = 0;
    header[19] = 0;
    header[20] = 1;
    header[21] = 0;
    header[22] = (byte) channel;
    header[23] = 0;
    header[24] = (byte) (srate & 0xff);
    header[25] = (byte) ((srate >> 8) & 0xff);
    header[26] = (byte) ((srate >> 16) & 0xff);
    header[27] = (byte) ((srate >> 24) & 0xff);
    header[28] = (byte) ((bitrate / 8) & 0xff);
    header[29] = (byte) (((bitrate / 8) >> 8) & 0xff);
    header[30] = (byte) (((bitrate / 8) >> 16) & 0xff);
    header[31] = (byte) (((bitrate / 8) >> 24) & 0xff);
    header[32] = (byte) ((channel * format) / 8);
    header[33] = 0;
    header[34] = 16;
    header[35] = 0;
    header[36] = 'd';
    header[37] = 'a';
    header[38] = 't';
    header[39] = 'a';
    header[40] = (byte) (dataLength & 0xff);
    header[41] = (byte) ((dataLength >> 8) & 0xff);
    header[42] = (byte) ((dataLength >> 16) & 0xff);
    header[43] = (byte) ((dataLength >> 24) & 0xff);

    return header;
  }

  /**
   * 默认写入的pcm数据是16000采样率，16bit，可以按照需要修改
   *
   * @param filePath
   * @param pcmData
   */
  public static boolean writeToFile(String filePath, byte[] pcmData) {
    BufferedOutputStream bos = null;
    try {
      bos = new BufferedOutputStream(new FileOutputStream(filePath));
      byte[] header = buildWavHeader(pcmData.length, 16000, 1, 16);
      bos.write(header, 0, 44);
      bos.write(pcmData);
      bos.close();
      return true;
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      if (bos != null) {
        try {
          bos.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }

    return false;
  }

  /**
   * 增加延时静音
   *
   * @param filePath 音频地址
   * @param tmpDirPath 临时目录地址
   * @param delayTime 延时时长，单位毫秒
   * @return 最终文件地址
   * @throws Exception 异常
   */
  public static String delayWav(String filePath, String tmpDirPath, Long delayTime)
      throws Exception {
    byte[] bytes;
    if (filePath.startsWith("http")) {
      bytes = IoUtil.readBytes(URLUtil.getStream(new URL(filePath)));
    } else {
      bytes = FileUtil.readBytes(filePath);
    }
    List<Byte> resultByte =
        new ArrayList<>(Bytes.asList(Arrays.copyOfRange(bytes, 44, bytes.length)));
    LongStream.range(0, (long) (delayTime * 32)).forEach(x -> resultByte.add((byte) 0));
    String resultPath =
        Joiner.on(File.separator).join(Arrays.asList(tmpDirPath, IdUtil.simpleUUID() + ".wav"));
    writeToFile(resultPath, Bytes.toArray(resultByte));
    return resultPath;
  }

  public static void main(String[] args) throws Exception {
    System.out.println(delayWav("http://xxxx/xxx.wav", "C:\\Users\\huyi\\Desktop\\", 10000L));
  }
}

代码说明：

1、delayWav方法参数分别为wav音频文件地址（可以支持http的url地址）、临时文件目录地址、延时静音时长（单位毫秒）

2、对wav的要求默认为：采样率16K、单声道。

对需要处理的音频参数调整。

3、生成uuid的随机文件名，避免重复。