from typing import Literal

NoiseLevel = Literal["quiet", "normal", "noisy", "very_noisy"]

def classify_noise(db: float) -> NoiseLevel:
    """Classify a simple noise level in dB for a home environment."""
    if db < 35:
        return "quiet"
    if db < 55:
        return "normal"
    if db < 75:
        return "noisy"
    return "very_noisy"

if __name__ == "__main__":
    tests = [30, 45, 60, 80]
    for d in tests:
        print(d, "->", classify_noise(d))