esp32 – ESP-32 I2S configuration for INMP441 MEMS microphone?

I’m trying to capture audio from an INMP441 microphone (datasheet) using the following code:

#include 
#include 

#include 
#include 
#include 
#include 
#include 

#include 
#include 

#include "wifi.h"
#include "mqtt.h"

#define BUFLEN      2048
#define SAMP_RATE   8000

#define I2S_WS  GPIO_NUM_25
#define I2S_SD  GPIO_NUM_33
#define I2S_SCK GPIO_NUM_32

const static char *TAG = "app";

static i2s_chan_handle_t chan;
static esp_mqtt_client_handle_t client;

static void i2s_read_task(void *args)
{
    size_t n;
    char *buf = calloc(1, BUFLEN);

    ESP_ERROR_CHECK(i2s_channel_enable(chan));

    for (;;) {
        if (i2s_channel_read(chan, buf, BUFLEN, &n, 1000) == ESP_OK) {
            if (n > 0)
                esp_mqtt_client_publish(client, "snd", buf, n, 1, 0);
        } else
            printf("Read Task: i2s read failed\n");
    }

    free(buf);
    vTaskDelete(NULL);
}

static inline void i2s_init(void)
{
    i2s_chan_config_t chan_cfg = I2S_CHANNEL_DEFAULT_CONFIG(
        I2S_NUM_AUTO,
        I2S_ROLE_MASTER);

    ESP_ERROR_CHECK(i2s_new_channel(&chan_cfg, NULL, &chan));

    i2s_std_config_t std_cfg = {
        .clk_cfg = I2S_STD_CLK_DEFAULT_CONFIG(SAMP_RATE),
        .slot_cfg = I2S_STD_MSB_SLOT_DEFAULT_CONFIG(
            I2S_DATA_BIT_WIDTH_24BIT,
            I2S_SLOT_MODE_MONO),
        .gpio_cfg = {
            .ws = I2S_WS,
            .din = I2S_SD,
            .bclk = I2S_SCK,
            .dout = I2S_GPIO_UNUSED,
            .mclk = I2S_GPIO_UNUSED,
            .invert_flags = {
                .ws_inv = false,
                .bclk_inv = false,
                .mclk_inv = false
            }   
        }
    };  

    std_cfg.clk_cfg.mclk_multiple = I2S_MCLK_MULTIPLE_384;

    ESP_ERROR_CHECK(i2s_channel_init_std_mode(chan, &std_cfg));
}

void app_main(void)
{
    ESP_ERROR_CHECK(nvs_flash_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());

    wifi_connect();
    client = mqtt_init();

    i2s_init();
    xTaskCreate(i2s_read_task, "i2s_read_task", 4096, NULL, 5, NULL);

    for (;;)
        vTaskDelay(500 / portTICK_PERIOD_MS);
}

I’m getting sound, but with quite a bit of noise. I couldn’t find any examples that use the newer ESP-IDF. I’m using ESP-IDF v5.2.1.