WaveViewController.m

@import UIKit;
@import AVFoundation;

@class _UISiriWaveyView;

@protocol _UISiriWaveyViewDelegate <NSObject>
- (CGFloat)audioLevelForWaveyView:(_UISiriWaveyView *)waveyView;
@end

typedef NS_ENUM(NSInteger, _UISiriWaveyViewMode) {
    _UISiriWaveyViewModeSiri,
    _UISiriWaveyViewModeDictation
};

@interface _UISiriWaveyView : UIView
@property(nonatomic) _UISiriWaveyViewMode mode;
@property(weak, nonatomic) id<_UISiriWaveyViewDelegate> delegate;
- (BOOL)inDictationMode;
- (BOOL)inSiriMode;
- (void)start;
@end

@interface WaveViewController : UIViewController <_UISiriWaveyViewDelegate>

@property (weak, nonatomic) _UISiriWaveyView *waveyView;

@property (strong, nonatomic) AVAudioRecorder *recorder;

@end

@implementation WaveViewController

- (void)loadView {
    [super loadView];

    _UISiriWaveyView *waveyView = [[_UISiriWaveyView alloc] init];
    waveyView.delegate = self;
    waveyView.translatesAutoresizingMaskIntoConstraints = NO;
    self.waveyView = waveyView;
    [self.view addSubview:waveyView];

    NSDictionary *views = @{ @"wave" : waveyView };
    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[wave]|" options:0 metrics:nil views:views]];
    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[wave]|" options:0 metrics:nil views:views]];
}

- (void)viewDidLoad {
    [super viewDidLoad];

    AVAudioSession *session = [AVAudioSession sharedInstance];
    [session setCategory:AVAudioSessionCategoryRecord error:nil];
    [session setActive:YES error:nil];

    NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject] stringByAppendingPathComponent:@"recording.caf"];
    NSURL *url = [NSURL fileURLWithPath:path];
    NSDictionary *settings = @{ AVEncoderAudioQualityKey: @(AVAudioQualityMin), AVEncoderBitRateKey: @8, AVNumberOfChannelsKey: @2, AVSampleRateKey: @22000 };
    AVAudioRecorder *recorder = [[AVAudioRecorder alloc] initWithURL:url settings:settings error:nil];
    recorder.meteringEnabled = YES;
    self.recorder = recorder;

    [self.recorder prepareToRecord];

    self.view.backgroundColor = [UIColor blackColor];

    UITapGestureRecognizer *gestureRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(waveyViewTapped:)];
    [_waveyView addGestureRecognizer:gestureRecognizer];
}

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];

    [_waveyView start];
    [_recorder record];
}

- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];

    [_recorder stop];
    [_recorder deleteRecording];
}

- (void)waveyViewTapped:(UITapGestureRecognizer *)gestureRecognizer {
    _waveyView.mode = _waveyView.mode == _UISiriWaveyViewModeSiri ? _UISiriWaveyViewModeDictation : _UISiriWaveyViewModeSiri;
}

- (CGFloat)audioLevelForWaveyView:(_UISiriWaveyView *)waveyView {
    [_recorder updateMeters];
    return [_recorder averagePowerForChannel:0];
}

@end