1. A method of determining an estimate for a noise-reduced value representing a portion of a noise-reduced speech signal, the method comprising: generating an alternative sensor signal using an alternative sensor other than an air conduction microphone; generating an air conduction microphone signal; determining whether a portion of the alternative sensor signal is corrupted by transient noise based in part on the air conduction microphone signal; and estimating the noise-reduced value based on the portion of the alternative sensor signal if the portion of the alternative sensor signal is determined to not be corrupted by transient noise.