Noise engine

LidAngleSensor/AppDelegate.m

@@ -9,17 +9,20 @@
 #import "LidAngleSensor.h"
 #import "CreakAudioEngine.h"
 #import "ThereminAudioEngine.h"
+#import "NoiseAudioEngine.h"
 #import "NSLabel.h"
 
 typedef NS_ENUM(NSInteger, AudioMode) {
     AudioModeCreak,
-    AudioModeTheremin
+    AudioModeTheremin,
+    AudioModeNoise
 };
 
 @interface AppDelegate ()
 @property (strong, nonatomic) LidAngleSensor *lidSensor;
 @property (strong, nonatomic) CreakAudioEngine *creakAudioEngine;
 @property (strong, nonatomic) ThereminAudioEngine *thereminAudioEngine;
+@property (strong, nonatomic) NoiseAudioEngine *noiseAudioEngine;
 @property (strong, nonatomic) NSLabel *angleLabel;
 @property (strong, nonatomic) NSLabel *statusLabel;
 @property (strong, nonatomic) NSLabel *velocityLabel;
@@ -120,9 +123,10 @@ - (void)createWindow {
 
     // Create mode selector
     self.modeSelector = [[NSSegmentedControl alloc] init];
-    [self.modeSelector setSegmentCount:2];
+    [self.modeSelector setSegmentCount:3];
     [self.modeSelector setLabel:@"Creak" forSegment:0];
     [self.modeSelector setLabel:@"Theremin" forSegment:1];
+    [self.modeSelector setLabel:@"Noise" forSegment:2];
     [self.modeSelector setSelectedSegment:0]; // Default to creak
     [self.modeSelector setTarget:self];
     [self.modeSelector setAction:@selector(modeChanged:)];
@@ -188,8 +192,9 @@ - (void)initializeLidSensor {
 - (void)initializeAudioEngines {
     self.creakAudioEngine = [[CreakAudioEngine alloc] init];
     self.thereminAudioEngine = [[ThereminAudioEngine alloc] init];
+    self.noiseAudioEngine = [[NoiseAudioEngine alloc] init];
 
-    if (self.creakAudioEngine && self.thereminAudioEngine) {
+    if (self.creakAudioEngine && self.thereminAudioEngine && self.noiseAudioEngine) {
         [self.audioStatusLabel setStringValue:@""];
     } else {
         [self.audioStatusLabel setStringValue:@"Audio initialization failed"];
@@ -247,6 +252,8 @@ - (id)currentAudioEngine {
             return self.creakAudioEngine;
         case AudioModeTheremin:
             return self.thereminAudioEngine;
+        case AudioModeNoise:
+            return self.noiseAudioEngine;
         default:
             return self.creakAudioEngine;
     }
@@ -302,6 +309,7 @@ - (void)updateAngleDisplay {
                     double volume = [currentEngine currentVolume];
                     [self.audioStatusLabel setStringValue:[NSString stringWithFormat:@"Freq: %.1f Hz, Vol: %.2f", frequency, volume]];
                 }
+                // TODO: noise
             }
         }
 

LidAngleSensor/NoiseAudioEngine.h

@@ -0,0 +1,56 @@
+//
+//  NoiseAudioEngine.h
+//  LidAngleSensor
+//
+//  Created by Sam on 2025-09-06.
+//
+
+#import <Foundation/Foundation.h>
+#import <AVFoundation/AVFoundation.h>
+
+/**
+ * Synthesized filtered noise
+ *
+ * Generate random noise, and filter it with a second order low pass filter, with a high quality
+ * factor (Q) and a cutoff frequency mapped to the lid angle.
+ * Biquad coeffs are updated with bilinear transform so that filter remains stable
+ *
+ * Most of the code was copied from from ThereminAudioEngine.m
+ */
+@interface NoiseAudioEngine : NSObject
+
+@property (nonatomic, assign, readonly) BOOL isEngineRunning;
+@property (nonatomic, assign, readonly) double currentVelocity;
+@property (nonatomic, assign, readonly) double currentFrequency;
+@property (nonatomic, assign, readonly) double currentVolume;
+
+/**
+ * Initialize the audio engine.
+ * @return Initialized engine instance, or nil if initialization failed
+ */
+- (instancetype)init;
+
+/**
+ * Start the audio engine and begin tone generation.
+ */
+- (void)startEngine;
+
+/**
+ * Stop the audio engine and halt tone generation.
+ */
+- (void)stopEngine;
+
+/**
+ * Update  based on new lid angle measurement.
+ * This method calculates frequency mapping and volume based on movement.
+ * @param lidAngle Current lid angle in degrees
+ */
+- (void)updateWithLidAngle:(double)lidAngle;
+
+/**
+ * Manually set the angular velocity (for testing purposes).
+ * @param velocity Angular velocity in degrees per second
+ */
+- (void)setAngularVelocity:(double)velocity;
+
+@end