【swift】AVAudioEngineでハウリングを抑える方法

Iphoneのマイクで拾った声を、AVAudioEngineでbluetoothスピーカーから出力しようとした時に、ボリュームを大きくするとハウリングしてしまいます。このハウリングを抑える方法がありませんでしょうか？

swift5
1import UIKit
2import AVFoundation
3
4class ViewController: UIViewController {
5    var audioEngine = AVAudioEngine()
6    override func viewDidLoad() {
7        super.viewDidLoad()
8        
9        self.view.backgroundColor = UIColor.yellow
10        
11        AudioSession()
12        
13        ChangeMicState()
14        MicSlider()
15        
16    }
17    //MARK:- Audio
18    func AudioSession(){
19        try! AVAudioSession.sharedInstance().setCategory(.playAndRecord,mode: .videoChat,options: .allowBluetoothA2DP)
20        
21        let input = audioEngine.inputNode
22        let output = audioEngine.mainMixerNode
23        let format = audioEngine.inputNode.inputFormat(forBus: 0)
24        
25        audioEngine.connect(input,to:output,format: format)
26        try! audioEngine.start()
27    }
28    //MARK:- Objects
29    func ChangeMicState(){
30        let changeMicState = UISwitch(frame: CGRect(x: 50, y: 50, width: 100, height: 50))
31        changeMicState.addTarget(self, action: #selector(sw(sender:)), for: .valueChanged)
32        self.view.addSubview(changeMicState)
33    }
34    @objc func sw(sender:UISwitch){
35        if sender.isOn{
36            try! audioEngine.start()
37        }else{
38            audioEngine.stop()
39        }
40    }
41    func MicSlider(){
42        let micSlider = UISlider(frame: CGRect(x: 50, y: 100, width: self.view.frame.width - 100, height: 30))
43        micSlider.addTarget(self, action: #selector(mic(sender:)), for: .valueChanged)
44        self.view.addSubview(micSlider)
45    }
46    @objc func mic(sender:UISlider){
47        print(sender.value)
48        audioEngine.inputNode.volume = sender.value * 100
49    }
50}