Time-varying scent determined by audio-meaningful events, such as gun firing, in an audio signal is generated by first computing a spectrogram thereof. A fingerprint, each having feature points, can be extracted from the spectrogram over a time window. The plurality of feature points is hashed to give a hash code. A sequence of hash codes obtained over multiple time windows is correlated with predetermined hash-code segments of known audio-meaningful events stored in a database. A matched audio-meaningful event having a highest correlation is identified. The scent-generating recipe corresponding to the matched audio-meaningful event is retrieved. Atomizers are used to vaporize scent-generating substances to generate the time-variant scent. Since the hash code has a fixed length and a smaller size than the plurality of feature points, storage requirements of the database and computation requirements of correlation calculation are reduced by using the hash code rather than the plurality of feature points.