kotlin: audioTrack delay 2s play has no effect

I'm using AudioTrack to play a series of audio data with 2s delay, but has no effect, the audio still play immediately, HERE IS MY CODE:

private fun delayOutput() {
    CoroutineScope(Dispatchers.Default).launch {
        withContext(Dispatchers.IO) {
            delay(2000)

            while (isRecording) {
                val item = if (cachedBuffers.isNotEmpty()) {
                    cachedBuffers.first()
                } else {
                    null
                }
                if (item != null) {
                    var writeRes: Int? = 0
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                        if (item is ShortArray) {
                            writeRes = audioTrack?.write(item, 0, item.size, WRITE_NON_BLOCKING)
                        }
                    }
                    cachedBuffers.removeAt(0)
                }
                delay(100)
            }
        }
    }

}

I print buffer's read time, it really is about 2s delay when write to audioTrack, i have no idea what's the matter.

I find the reason, because audiotrack is not init correct, correct code beside:

audioTrack = AudioTrack(AudioManager.STREAM_SYSTEM, sampleRateInHz, AudioFormat.CHANNEL_OUT_MONO, audioFormat, bufferSize * 4, AudioTrack.MODE_STREAM)