Flutter can't play audio with recording

I am making a hearing aid application in flutter for those who can't hear properly, idea is sound that microphone get user can change its frequency, pitch other settings using slider or something else, and the speaker play that audio with processed settings, issue i am facing is flutter first record audio then play it how i make it that it directly play audio from microphone to speaker, speaker could be of mobile/headset.

I am expecting to play audio along with microphone one.

import 'dart:async';
import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'package:flutter_sound/flutter_sound.dart';
import 'package:permission_handler/permission_handler.dart';

class VoiceChanger extends StatefulWidget {
  @override
  _VoiceChangerState createState() => _VoiceChangerState();
}

class _VoiceChangerState extends State<VoiceChanger> {
  late final StreamController<Uint8List> _audioStreamController;

  FlutterSoundRecorder? _recorder;
  FlutterSoundPlayer? _player;
  bool isRecording = false;
  bool isPlayingBack = false;

  @override
  void initState() {
    super.initState();
    _recorder = FlutterSoundRecorder();
    _player = FlutterSoundPlayer();
    _audioStreamController = StreamController<Uint8List>();
    initAudio();
  }

  Future<void> initAudio() async {
    await _recorder!.openRecorder();
    await _player!.openPlayer();
    await _player!.setVolume(1.0);
  }

  Future<void> startRecording() async {
    if (await Permission.microphone.request().isGranted) {
      // Start recording to a stream
      await _recorder!.startRecorder(
        toStream: _audioStreamController.sink,
        codec: Codec.pcm16,
      );

      // Listen to the stream and play audio data in real-time
      _audioStreamController.stream.listen((data) async {
        // Ensure playback continues smoothly
        if (!isPlayingBack) {
          isPlayingBack = true;
          await _player!.startPlayer(
            fromDataBuffer: data,
            codec: Codec.pcm16,
            whenFinished: () {
              isPlayingBack = false; // Set playing flag to false when finished
            },
          );
        } else {
          // Feed the new audio data to the player without interruption
          await _player!.feedFromStream(data);
        }
      });

      setState(() {
        isRecording = true;
      });
    } else {
      print("Microphone permission is not granted");
    }
  }

  Future<void> stopRecording() async {
    await _recorder!.stopRecorder();
    setState(() {
      isRecording = false;
      isPlayingBack = false; // Stop playback
    });
  }

  @override
  void dispose() {
    _recorder?.closeRecorder();
    _player?.closePlayer();
    _audioStreamController.close(); // Ensure stream is closed
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Voice Changer'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            ElevatedButton(
              onPressed: isRecording ? stopRecording : startRecording,
              child: Text(isRecording ? 'Stop Recording' : 'Start Recording'),
            ),
          ],
        ),
      ),
    );
  }
}