iOS - Detect Blow into Mic and convert the results! (swift) - ios

Question

I need to develop an iOS App in swift which detects a blow in the microphone from a user. This has to be a Challenge-Game where two players have to blow into the iPhone mic one after the other. The decibel values should be measured and converted in meter or kilometer so I can determine a winner. The player which "blows further" (player1: 50km, player2: 70km) wins.
Is this a possible implementation?
I have this code in swift and I don't know how to proceed:
import Foundation
import UIKit
import AVFoundation
import CoreAudio
class ViewController: UIViewController {
// #IBOutlet weak var mainImage: UIImageView!
var recorder: AVAudioRecorder!
var levelTimer = NSTimer()
var lowPassResults: Double = 0.0
override func viewDidLoad() {
super.viewDidLoad()
let url = NSURL.fileURLWithPath("dev/null")
//numbers are automatically wrapped into NSNumber objects, so I simplified that to [NSString : NSNumber]
var settings : [NSString : NSNumber] = [AVSampleRateKey: 44100.0, AVFormatIDKey: kAudioFormatAppleLossless, AVNumberOfChannelsKey: 1, AVEncoderAudioQualityKey: AVAudioQuality.Max.rawValue]
var error: NSError?
// mainImage?.image = UIImage(named: "flyForReal.png");
recorder = AVAudioRecorder(URL:url, settings:settings, error:&error)
if((recorder) != nil){
recorder.prepareToRecord()
recorder.meteringEnabled = true
recorder.record()
levelTimer = NSTimer.scheduledTimerWithTimeInterval(0.05, target: self, selector: Selector("levelTimerCallback"), userInfo: nil, repeats: true)
}
else{
NSLog("%#", "Error");
}
}
func levelTimerCallback(timer:NSTimer) {
recorder.updateMeters()
let ALPHA: Double = 0.05
var peakPowerForChannel = pow(Double(10), (0.05 * Double(recorder.peakPowerForChannel(0))))
lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * lowPassResults;
if(lowPassResults > 0.95){
NSLog("#Mic blow detected");
}
NSLog("#Average input: %f Peak input: %f Low pass results: %f", recorder.averagePowerForChannel(0), recorder.peakPowerForChannel(0), lowPassResults);
}
}
Thanks ahead!

Answer 1

I converted Andrew's answer to Swift 4:
import Foundation
import UIKit
import AVFoundation
import CoreAudio
class ViewController: UIViewController {
var recorder: AVAudioRecorder!
var levelTimer = Timer()
let LEVEL_THRESHOLD: Float = -10.0
override func viewDidLoad() {
super.viewDidLoad()
let documents = URL(fileURLWithPath: NSSearchPathForDirectoriesInDomains(FileManager.SearchPathDirectory.documentDirectory, FileManager.SearchPathDomainMask.userDomainMask, true)[0])
let url = documents.appendingPathComponent("record.caf")
let recordSettings: [String: Any] = [
AVFormatIDKey: kAudioFormatAppleIMA4,
AVSampleRateKey: 44100.0,
AVNumberOfChannelsKey: 2,
AVEncoderBitRateKey: 12800,
AVLinearPCMBitDepthKey: 16,
AVEncoderAudioQualityKey: AVAudioQuality.max.rawValue
]
let audioSession = AVAudioSession.sharedInstance()
do {
try audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord)
try audioSession.setActive(true)
try recorder = AVAudioRecorder(url:url, settings: recordSettings)
} catch {
return
}
recorder.prepareToRecord()
recorder.isMeteringEnabled = true
recorder.record()
levelTimer = Timer.scheduledTimer(timeInterval: 0.02, target: self, selector: #selector(levelTimerCallback), userInfo: nil, repeats: true)
}
#objc func levelTimerCallback() {
recorder.updateMeters()
let level = recorder.averagePower(forChannel: 0)
let isLoud = level > LEVEL_THRESHOLD
// do whatever you want with isLoud
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}

Answer 2

Close. You have a couple of issues. Your selector call crashes the app because you're not passing an argument and levelTimerCallback() expects one.
averagePowerPerChannel seems to give me a more real-time metering so I used that instead of peakPowerPerChannel
Also, you need to set up an audio session. I wasn't really sure what all that math was about, so I just got rid of it here. I've pasted the entire view controller below for basic mic detection.
import Foundation
import UIKit
import AVFoundation
import CoreAudio
class ViewController: UIViewController {
var recorder: AVAudioRecorder!
var levelTimer = NSTimer()
var lowPassResults: Double = 0.0
override func viewDidLoad() {
super.viewDidLoad()
//make an AudioSession, set it to PlayAndRecord and make it active
var audioSession:AVAudioSession = AVAudioSession.sharedInstance()
audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord, error: nil)
audioSession.setActive(true, error: nil)
//set up the URL for the audio file
var documents: AnyObject = NSSearchPathForDirectoriesInDomains( NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true)[0]
var str = documents.stringByAppendingPathComponent("recordTest.caf")
var url = NSURL.fileURLWithPath(str as String)
// make a dictionary to hold the recording settings so we can instantiate our AVAudioRecorder
var recordSettings: [NSObject : AnyObject] = [AVFormatIDKey:kAudioFormatAppleIMA4,
AVSampleRateKey:44100.0,
AVNumberOfChannelsKey:2,AVEncoderBitRateKey:12800,
AVLinearPCMBitDepthKey:16,
AVEncoderAudioQualityKey:AVAudioQuality.Max.rawValue
]
//declare a variable to store the returned error if we have a problem instantiating our AVAudioRecorder
var error: NSError?
//Instantiate an AVAudioRecorder
recorder = AVAudioRecorder(URL:url, settings: recordSettings, error: &error)
//If there's an error, print that shit - otherwise, run prepareToRecord and meteringEnabled to turn on metering (must be run in that order)
if let e = error {
println(e.localizedDescription)
} else {
recorder.prepareToRecord()
recorder.meteringEnabled = true
//start recording
recorder.record()
//instantiate a timer to be called with whatever frequency we want to grab metering values
self.levelTimer = NSTimer.scheduledTimerWithTimeInterval(0.02, target: self, selector: Selector("levelTimerCallback"), userInfo: nil, repeats: true)
}
}
//This selector/function is called every time our timer (levelTime) fires
func levelTimerCallback() {
//we have to update meters before we can get the metering values
recorder.updateMeters()
//print to the console if we are beyond a threshold value. Here I've used -7
if recorder.averagePowerForChannel(0) > -7 {
print("Dis be da level I'm hearin' you in dat mic ")
println(recorder.averagePowerForChannel(0))
println("Do the thing I want, mofo")
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}