AWARE: Ambient Noise

This sensor module captures ambient sound levels (decibels) and classifies audio using Apple's SoundAnalysis framework. It provides two concurrent data streams: continuous decibel measurements and sound classification labels with confidence scores.

Requirements

iOS 15 or later

Installation

1. Open Package Manager Windows

   • Open Xcode -> Select Menu Bar -> File -> App Package Dependencies...

2. Find the package using the manager

   • Select Search Package URL and type https://github.com/awareframework/com.awareframework.ios.sensor.ambientnoise.git

3. Import the package into your target.

4. Add NSMicrophoneUsageDescription to your Info.plist.

Public functions

AmbientNoiseSensor

• init(_ config: AmbientNoiseSensor.Config): Initializes the sensor with the given configuration.
• start(): Starts audio recording and analysis.
• stop(): Stops audio processing and releases the audio engine.
• sync(force:): Syncs stored data to the configured host.
• set(label:): Sets a custom label applied to all subsequent data points.
• availableMicrophoneInputs() -> [AmbientNoiseMicrophoneInput]: Returns the list of available microphone inputs.
• refreshCurrentMicrophone(): Updates the current microphone info in the config.

AmbientNoiseSensor.Config

Class to hold the configuration of the sensor.

Fields

• sensorObserver: AmbientNoiseSensorObserver?: Callback for live data updates.
• activateAmbientNoiseSensor: Bool: Enable decibel measurement. (default = true)
• activateAudioClassificationSensor: Bool: Enable sound classification via SoundAnalysis. (default = true)
• audioClassifierModel: MLModel?: Custom Core ML classifier. Uses the built-in iOS classifier when nil. (default = nil)
• storeOnlyTopK: Int?: If set, only the top-K classifications by confidence are stored per analysis window. (default = nil = store all)
• preferredInputUID: String: UID of the preferred microphone input. Leave empty to use the system default.
• bufferSize: UInt32: AVAudioEngine tap buffer size. (default = 8192)
• onBus: Int: Audio engine input bus. (default = 0)
• enabled: Bool: Sensor is enabled or not. (default = false)
• debug: Bool: Enable/disable logging. (default = false)
• label: String: Label for the data. (default = "")
• deviceId: String: Id of the device associated with the events. (default = "")
• dbEncryptionKey: Encryption key for the database. (default = nil)
• dbType: Engine: Which db engine to use for saving data. (default = Engine.DatabaseType.NONE)
• dbPath: String: Path of the database.
• dbHost: String: Host for syncing the database. (default = nil)

Broadcasts

Fired Broadcasts

• AmbientNoiseSensor.ACTION_AWARE_AMBIENT_NOISE: fired when a new decibel measurement is recorded.
• AmbientNoiseSensor.ACTION_AWARE_AUDIO_LABEL: fired when a new audio classification result is available.

Received Broadcasts

• AmbientNoiseSensor.ACTION_AWARE_AMBIENT_NOISE_START: received broadcast to start the sensor.
• AmbientNoiseSensor.ACTION_AWARE_AMBIENT_NOISE_STOP: received broadcast to stop the sensor.
• AmbientNoiseSensor.ACTION_AWARE_AMBIENT_NOISE_SYNC: received broadcast to send sync attempt to the host.
• AmbientNoiseSensor.ACTION_AWARE_AMBIENT_NOISE_SET_LABEL: received broadcast to set the data label. Label is expected in the AmbientNoiseSensor.EXTRA_LABEL field of the notification userInfo.

Data Representations

AmbientNoiseData

Contains the decibel measurement.

Field	Type	Description
db	Double	Sound level in decibels (dBFS)
label	String	Customizable label. Useful for data calibration or traceability
deviceId	String	AWARE device UUID
timestamp	Int64	Unixtime milliseconds since 1970
timezone	Int	Timezone of the device
os	String	Operating system of the device (iOS)

AudioLabelData

Contains a sound classification result.

Field	Type	Description
audioLabel	String	Sound classification label (e.g., "music", "speech", "silence")
confidence	Double	Confidence score of the classification [0.0–1.0]
label	String	Customizable label. Useful for data calibration or traceability
deviceId	String	AWARE device UUID
timestamp	Int64	Unixtime milliseconds since 1970
timezone	Int	Timezone of the device
os	String	Operating system of the device (iOS)

Example usage

import com_awareframework_ios_sensor_ambientnoise

let sensor = AmbientNoiseSensor(AmbientNoiseSensor.Config().apply { config in
    config.sensorObserver = Observer()
    config.activateAmbientNoiseSensor = true
    config.activateAudioClassificationSensor = true
    config.storeOnlyTopK = 3
    config.debug = true
})

sensor.start()

// Later...
sensor.stop()

class Observer: AmbientNoiseSensorObserver {
    func onAmbientNoiseChanged(data: AmbientNoiseData) {
        print("Decibels:", data.db)
    }

    func onAudioLabelChanged(data: AudioLabelData) {
        print("Label:", data.audioLabel, "Confidence:", data.confidence)
    }
}

Author

Yuuki Nishiyama (The University of Tokyo), nishiyama@csis.u-tokyo.ac.jp

Related Links

• Apple | SoundAnalysis
• Apple | AVAudioEngine

License

Copyright (c) 2018 AWARE Mobile Context Instrumentation Middleware/Framework (http://www.awareframework.com)

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.