如何在 C 中使 Siren 发声？

Posted 2023-02-25

【中文标题】如何在 C 中使 Siren 发声？

【英文标题】：How can I make Siren sound in C?

【发布时间】：2021-05-13 18:15:21

【问题描述】：

我想发出每 0.65 秒频率变化 960Hz 和 770Hz 的警笛声。 （在 8 秒 Wav 文件中） 但我不知道如何构建上面写的函数。 我尝试在每个时期都使用'for(...=0; ...

直截了当地说，我想知道如何使频率每 0.65 秒可变为 960Hz 和 770Hz。 如果您给我建议以实现我的最终目标，我将不胜感激。

由于我的英语不好，如果你很难理解我的问题，请评论我。

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <iostream> 

#pragma once 
#define WAVE_FORMAT_UNKNOWN 0X0000; 
#define WAVE_FORMAT_PCM 0X0001;
#define WAVE_FORMAT_MS_ADPCM 0X0002; 
#define WAVE_FORMAT_IEEE_FLOAT 0X0003; 
#define WAVE_FORMAT_ALAW 0X0006; 
#define WAVE_FORMAT_MULAW 0X0007; 
#define WAVE_FORMAT_IMA_ADPCM 0X0011; 
#define WAVE_FORMAT_YAMAHA_ADPCM 0X0016;
#define WAVE_FORMAT_GSM 0X0031; 
#define WAVE_FORMAT_ITU_ADPCM 0X0040; 
#define WAVE_FORMAT_MPEG 0X0050;
#define WAVE_FORMAT_EXTENSIBLE 0XFFFE;


#define DURATION 8 
#define SAMPLE_RATE 48000
#define CHANNEL 2
#define BIT_RATE 16

typedef struct 
    unsigned char ChunkID[4]; // Contains the letters "RIFF" in ASCII form 
    unsigned int ChunkSize; // This is the size of the rest of the chunk following this number 
    unsigned char Format[4]; // Contains the letters "WAVE" in ASCII form 
 RIFF;

typedef struct 
    unsigned char ChunkID[4]; // Contains the letters "fmt " in ASCII form 
    unsigned int ChunkSize; // 16 for PCM. This is the size of the rest of the Subchunk which follows this number. 
    unsigned short AudioFormat; // PCM = 1 
    unsigned short NumChannels; // Mono = 1, Stereo = 2, etc. 
    unsigned int SampleRate; // 8000, 44100, etc. 
    unsigned int AvgByteRate; // SampleRate * NumChannels * BitsPerSample/8 
    unsigned short BlockAlign; // NumChannels * BitsPerSample/8 
    unsigned short BitPerSample; // 8 bits = 8, 16 bits = 16, etc 
 FMT;

typedef struct 
    char ChunkID[4]; // Contains the letters "data" in ASCII form 
    unsigned int ChunkSize; // NumSamples * NumChannels * BitsPerSample/8 
 DATA;

typedef struct 
    RIFF Riff;
    FMT Fmt;
    DATA Data;
 WAVE_HEADER;



int main() 
    FILE* f_out;
    f_out = fopen("D:\\test.wav", "wb");

    WAVE_HEADER header;
    memcpy(header.Riff.ChunkID, "RIFF", 4);
    header.Riff.ChunkSize = DURATION * SAMPLE_RATE * CHANNEL * BIT_RATE / 8 + 36;
    memcpy(header.Riff.Format, "WAVE", 4);

    memcpy(header.Fmt.ChunkID, "fmt ", 4);
    header.Fmt.ChunkSize = 0x10;
    header.Fmt.AudioFormat = WAVE_FORMAT_PCM;
    header.Fmt.NumChannels = CHANNEL;
    header.Fmt.SampleRate = SAMPLE_RATE;
    header.Fmt.AvgByteRate = SAMPLE_RATE * CHANNEL * BIT_RATE / 8;
    header.Fmt.BlockAlign = CHANNEL * BIT_RATE / 8;
    header.Fmt.BitPerSample = BIT_RATE;

    memcpy(header.Data.ChunkID, "data", 4);
    header.Data.ChunkSize = DURATION * SAMPLE_RATE * CHANNEL * BIT_RATE / 8;

    fwrite(&header, sizeof(header), 1, f_out);

    short y[2]; 
    double high_freq = 960;
    double low_freq = 770;
    for (int i = 0; i < SAMPLE_RATE * DURATION; i++) 
        double level_l = (double)i / (SAMPLE_RATE * DURATION);
        double level_r = 1.0 - level_l;

        y[0] = (short)(30000 * sin(2 * 3.141592 * i * high_freq / SAMPLE_RATE) * level_l);
        y[1] = (short)(30000 * sin(2 * 3.141592 * i * low_freq / SAMPLE_RATE) * level_r);
        fwrite(&y[0], sizeof(short), 1, f_out);
        fwrite(&y[1], sizeof(short), 1, f_out);
    


    fclose(f_out);
    return 0;

【参考方案1】：

您在交替的样本上输出两个频率中的每一个。即左声道一个频率的稳定音，右声道另一个频率的稳定音。

我们需要做的是保持在给定的子持续时间内相同的频率并在它们之间翻转。而且，相同的频率被馈送到两个频道[尽管音量不同]。

这里有一个轻微的重构可以做到这一点。有注释。

我不确定您使用的级别（例如 level_l 和 level_r）。我认为它们相同听起来更好（即警报越来越近），所以我将level_r 设为level_l 作为一个选项。但是，我保留了原始的 L/R 缩放比例。

编辑：听完上面的内容后，当我缩短子持续时间时，警报器听起来更像是真正的 [欧洲] 警报器。我不确定它仍然是 0.65 秒，但听起来更好[对我来说]

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
//#include <iostream>
#include <string.h>
#include <math.h>

//#pragma once
#define WAVE_FORMAT_UNKNOWN 0X0000;
#define WAVE_FORMAT_PCM 0X0001;
#define WAVE_FORMAT_MS_ADPCM 0X0002;
#define WAVE_FORMAT_IEEE_FLOAT 0X0003;
#define WAVE_FORMAT_ALAW 0X0006;
#define WAVE_FORMAT_MULAW 0X0007;
#define WAVE_FORMAT_IMA_ADPCM 0X0011;
#define WAVE_FORMAT_YAMAHA_ADPCM 0X0016;
#define WAVE_FORMAT_GSM 0X0031;
#define WAVE_FORMAT_ITU_ADPCM 0X0040;
#define WAVE_FORMAT_MPEG 0X0050;
#define WAVE_FORMAT_EXTENSIBLE 0XFFFE;

#define DURATION 8
#define SAMPLE_RATE 48000
#define CHANNEL 2
#define BIT_RATE 16

typedef struct 
    unsigned char ChunkID[4];           // Contains the letters "RIFF" in ASCII form
    unsigned int ChunkSize;             // This is the size of the rest of the chunk following this number
    unsigned char Format[4];            // Contains the letters "WAVE" in ASCII form
 RIFF;

typedef struct 
    unsigned char ChunkID[4];           // Contains the letters "fmt " in ASCII form
    unsigned int ChunkSize;             // 16 for PCM. This is the size of the rest of the Subchunk which follows this number.
    unsigned short AudioFormat;         // PCM = 1
    unsigned short NumChannels;         // Mono = 1, Stereo = 2, etc.
    unsigned int SampleRate;            // 8000, 44100, etc.
    unsigned int AvgByteRate;           // SampleRate * NumChannels * BitsPerSample/8
    unsigned short BlockAlign;          // NumChannels * BitsPerSample/8
    unsigned short BitPerSample;        // 8 bits = 8, 16 bits = 16, etc
 FMT;

typedef struct 
    char ChunkID[4];                    // Contains the letters "data" in ASCII form
    unsigned int ChunkSize;             // NumSamples * NumChannels * BitsPerSample/8
 DATA;

typedef struct 
    RIFF Riff;
    FMT Fmt;
    DATA Data;
 WAVE_HEADER;

int
main()

    FILE *f_out;

#if 0
    f_out = fopen("D:\\test.wav", "wb");
#else
    f_out = fopen("test.wav", "wb");
#endif

    WAVE_HEADER header;

    memcpy(header.Riff.ChunkID, "RIFF", 4);
    header.Riff.ChunkSize = DURATION * SAMPLE_RATE * CHANNEL * BIT_RATE / 8 + 36;
    memcpy(header.Riff.Format, "WAVE", 4);

    memcpy(header.Fmt.ChunkID, "fmt ", 4);
    header.Fmt.ChunkSize = 0x10;
    header.Fmt.AudioFormat = WAVE_FORMAT_PCM;
    header.Fmt.NumChannels = CHANNEL;
    header.Fmt.SampleRate = SAMPLE_RATE;
    header.Fmt.AvgByteRate = SAMPLE_RATE * CHANNEL * BIT_RATE / 8;
    header.Fmt.BlockAlign = CHANNEL * BIT_RATE / 8;
    header.Fmt.BitPerSample = BIT_RATE;

    memcpy(header.Data.ChunkID, "data", 4);
    header.Data.ChunkSize = DURATION * SAMPLE_RATE * CHANNEL * BIT_RATE / 8;

    fwrite(&header, sizeof(header), 1, f_out);

    short y[2];
    double high_freq = 960;
    double low_freq = 770;

#if 0
    for (int i = 0; i < SAMPLE_RATE * DURATION; i++) 
        double level_l = (double) i / (SAMPLE_RATE * DURATION);
        double level_r = 1.0 - level_l;

        y[0] = (short) (30000 * sin(2 * 3.141592 * i * high_freq / SAMPLE_RATE) * level_l);
        y[1] = (short) (30000 * sin(2 * 3.141592 * i * low_freq / SAMPLE_RATE) * level_r);
        fwrite(&y[0], sizeof(short), 1, f_out);
        fwrite(&y[1], sizeof(short), 1, f_out);
    
#endif

#if 1
    // number of samples to flip on
#if 0
    int flipfreq = (SAMPLE_RATE * 65) / 100;
#else
    int flipfreq = (SAMPLE_RATE * 65) / 200;
#endif

    // current frequency to use
    int curtyp = 0;

    for (int i = 0; i < SAMPLE_RATE * DURATION; i++) 
        // after 0.65 seconds, change the frequency
        if ((i % flipfreq) == 0)
            curtyp = ! curtyp;

        // use the frequency for this period
        double cur_freq = curtyp ? high_freq : low_freq;

        double level_l = (double) i / (SAMPLE_RATE * DURATION);
#if 1
        double level_r = 1.0 - level_l;
#else
        double level_r = level_l;
#endif

        y[0] = (short) (30000 * sin(2 * 3.141592 * i * cur_freq / SAMPLE_RATE) * level_l);
        y[1] = (short) (30000 * sin(2 * 3.141592 * i * cur_freq / SAMPLE_RATE) * level_r);
        fwrite(&y[0], sizeof(short), 1, f_out);
        fwrite(&y[1], sizeof(short), 1, f_out);
    
#endif

    fclose(f_out);
    return 0;

【讨论】：

感谢您的回答！！我还有 2 个问题。 1）如果我想使左（或右）声音的时间发散（如1毫秒）比另一侧声音，我应该如何构建代码？例如，left sound(y[0]) 可以比正常功能早 1 秒听到（你回答了哪个） 2) '(SAMPLE_RATE * 65) / 200' 中的 '200' 的意思是什么？？