头文件：

#ifndef __CAPTURE_AUDIO__
#define __CAPTURE_AUDIO__

#include <functional>
#include <windows.h>
#pragma comment(lib, "winmm.lib")

class CaptureAudio
{
public:
	CaptureAudio();
	~CaptureAudio();

public:
	bool Init(const std::function<void(unsigned char* pPcmAudioData, long nLen)>& pFunc);
	void Uninit();

private:
	bool Capture();

private:
	static unsigned int __stdcall Process(void* args);

private:
	unsigned char* m_pAudioData = nullptr;

private:
	HANDLE m_threadRecv = INVALID_HANDLE_VALUE;
	HANDLE m_threadEvent = INVALID_HANDLE_VALUE;

private:
	WAVEHDR m_wHdr; //采集音频时包含数据缓存的结构体
	HWAVEIN m_hWaveIn;//输入设备

private:
	std::function<void(unsigned char* pPcmAudioData, long nLen)> m_pFunc;
};

#endif

源文件：

#include "CaptureAudio.h"
#include <chrono>
#include <thread>

using namespace std;

CaptureAudio::CaptureAudio()
{
	while (!m_pAudioData) {
		try{
			m_pAudioData = new unsigned char[1024 * 1024];
		}
		catch (...){}
	}
}
CaptureAudio::~CaptureAudio()
{
	if (m_pAudioData) {
		delete[]m_pAudioData;
		m_pAudioData = nullptr;
	}
}


bool CaptureAudio::Init(const std::function<void(unsigned char* pPcmAudioData, long nLen)>& pFunc)
{
	UINT nDev = waveInGetNumDevs();
	if (nDev == 0) {
		return false;
	}


	WAVEFORMATEX waveform; //采集音频的格式，结构体
	waveform.wFormatTag = WAVE_FORMAT_PCM;//声音格式为PCM
	waveform.nSamplesPerSec = 48000;//采样率，16000次/秒
	waveform.wBitsPerSample = 16;//采样比特，16bits/次
	waveform.nChannels = 1;//采样声道数，2声道
	waveform.nAvgBytesPerSec = 16000;//每秒的数据率，就是每秒能采集多少字节的数据
	waveform.nBlockAlign = 2;//一个块的大小，采样bit的字节数乘以声道数
	waveform.cbSize = 0;//一般为0
	MMRESULT hResults = waveInOpen(&m_hWaveIn, WAVE_MAPPER, &waveform, (DWORD_PTR)0, (DWORD_PTR)this, CALLBACK_NULL);//使用waveInOpen函数开启音频采集
	if (hResults != MMSYSERR_NOERROR) {
		return false;
	}

	m_threadEvent = CreateEvent(NULL, true, false, L"");
	m_threadRecv = (HANDLE)_beginthreadex(NULL, 0, Process, this, 0, NULL);

	m_pFunc = pFunc;
	return true;
}

void CaptureAudio::Uninit()
{
	if (m_threadRecv != INVALID_HANDLE_VALUE && m_threadEvent != INVALID_HANDLE_VALUE) {
		SetEvent(m_threadEvent);
		WaitForSingleObject(m_threadRecv, INFINITE);
		CloseHandle(m_threadRecv);
		CloseHandle(m_threadEvent);

		m_threadRecv = INVALID_HANDLE_VALUE;
		m_threadEvent = INVALID_HANDLE_VALUE;
	}

	waveInUnprepareHeader(m_hWaveIn, &m_wHdr, sizeof(WAVEHDR));
	waveInStop(m_hWaveIn);
	waveInClose(m_hWaveIn);
}

bool CaptureAudio::Capture()
{
	waveInUnprepareHeader(m_hWaveIn, &m_wHdr, sizeof(WAVEHDR));

	memset(m_pAudioData, 0, 1024 * 1024);
	m_wHdr.lpData = (LPSTR)m_pAudioData;
	m_wHdr.dwBufferLength = 1024 * 1024;
	m_wHdr.dwBytesRecorded = 0;
	m_wHdr.dwUser = 0;
	m_wHdr.dwFlags = WHDR_DONE;
	m_wHdr.dwLoops = 1;
	waveInPrepareHeader(m_hWaveIn, &m_wHdr, sizeof(WAVEHDR));//准备一个波形数据块头用于录音
	waveInAddBuffer(m_hWaveIn, &m_wHdr, sizeof(WAVEHDR));//指定波形数据块为录音输入缓存
	MMRESULT hResults = waveInStart(m_hWaveIn);//开始录音
	if (hResults != MMSYSERR_NOERROR) {
		return false;
	}
	std::this_thread::sleep_for(std::chrono::milliseconds(100));

	waveInReset(m_hWaveIn);

	if (m_pFunc) {
		m_pFunc(m_pAudioData, m_wHdr.dwBytesRecorded);
	}

	return true;
}

unsigned int CaptureAudio::Process(void* args)
{
	CaptureAudio* pThis = (CaptureAudio*)args;

	while (true) {
		if (WaitForSingleObject(pThis->m_threadEvent, 0) == WAIT_OBJECT_0) {
			break;
		}
		pThis->Capture();
	}
	return 0;
}

生成的文件pcm：