Swift SoundClassifier

What a sound is, using the classifier macOS already has.

import SoundClassifier

for window in try SoundClassifier.classify(fileAt: url) {
    print(window.start, window.top?.name ?? "—", window.top?.confidence ?? 0)
}

try SoundClassifier.knownClasses().count   // 303

Why

SNClassifySoundRequest(classifierIdentifier: .version1) — Apple's built-in classifier, already installed. No model to download, no network, no permission prompt. 303 classes: speech and its varieties (shouting, whispering, laughter, crying), animals, vehicles, tools, alarms, water, music, and the noises a room makes.

Deliberately not music analysis. swift-music-analysis measures BPM, key and structure; this answers "what is that noise". They overlap only in that both listen.

Two things the API will not tell you

The window is fixed at 3 seconds. Audio shorter than one window produces zero results and no error — which reads as "nothing in this audio" rather than "too short to ask". So a short file throws instead, naming both durations.

The confidences are not calibrated. Apple documents no meaning for them. They order results reliably and mean nothing in absolute terms: a 0.8 is not "80% likely", it is "more than the 0.6 beside it". minimumConfidence is a noise gate, not a probability threshold, and this package says so rather than implying otherwise by naming it one.

Labels stay exactly as the classifier returns them — dog_bark, not "Dog bark" — because renaming would make the printed name and the filterable label disagree. name does the prettifying at the point of printing.

Tested

7 tests on synthetic audio: the classifier is present without a download, the window really is 3 seconds, short audio is refused rather than silently empty, results come back strongest-first, and the confidence gate actually drops things.

Licence

MIT.