12. An article of manufacture including a non-transitory computer-readable storage medium, having stored thereon program instructions that, upon execution by a computing device, cause the computing device to perform operations comprising: selecting a first gender-specific speaker adaptation technique based on characteristics of a first set of feature vectors, wherein the first set of feature vectors correspond to a first unit of input speech, and wherein the first set of feature vectors are configured for use in automatic speech recognition (ASR) of the first unit of input speech, wherein the first gender-specific speaker adaptation technique is associated with a particular gender; modifying a second set of feature vectors based on the first gender-specific speaker adaptation technique, wherein the second set of feature vectors correspond to a second unit of input speech, and wherein the modified second set of feature vectors are configured for use in ASR of the second unit of input speech; based on characteristics of the second set of feature vectors and the first gender-specific speaker adaptation technique being associated with a particular gender, selecting a first speaker-dependent speaker adaptation technique that is associated with a particular speaker of the particular gender; and modifying a third set of feature vectors based on the first speaker-dependent speaker adaptation technique, wherein the third set of feature vectors correspond to a third unit of input speech, and wherein the modified third set of feature vectors are configured for use in ASR of the third unit of input speech.
12. An article of manufacture including a non-transitory computer-readable storage medium, having stored thereon program instructions that, upon execution by a computing device, cause the computing device to perform operations comprising: selecting a first gender-specific speaker adaptation technique based on characteristics of a first set of feature vectors, wherein the first set of feature vectors correspond to a first unit of input speech, and wherein the first set of feature vectors are configured for use in automatic speech recognition (ASR) of the first unit of input speech, wherein the first gender-specific speaker adaptation technique is associated with a particular gender; modifying a second set of feature vectors based on the first gender-specific speaker adaptation technique, wherein the second set of feature vectors correspond to a second unit of input speech, and wherein the modified second set of feature vectors are configured for use in ASR of the second unit of input speech; based on characteristics of the second set of feature vectors and the first gender-specific speaker adaptation technique being associated with a particular gender, selecting a first speaker-dependent speaker adaptation technique that is associated with a particular speaker of the particular gender; and modifying a third set of feature vectors based on the first speaker-dependent speaker adaptation technique, wherein the third set of feature vectors correspond to a third unit of input speech, and wherein the modified third set of feature vectors are configured for use in ASR of the third unit of input speech. 13. The article of manufacture of claim 12 , the operations further comprising: determining that (i) the third unit of input speech was originated proximate to a particular location, and (ii) the particular speaker is also associated with an environment-specific, speaker-dependent speaker adaptation technique, wherein the environment-specific, speaker-dependent speaker adaptation technique is associated with the particular location; selecting the environment-specific, speaker-dependent speaker adaptation technique; and modifying a fourth set of feature vectors based on the environment-specific, speaker-dependent speaker adaptation technique, wherein the fourth set of feature vectors correspond to a fourth unit of input speech, and wherein the modified fourth set of feature vectors are configured for use in ASR of the fourth unit of input speech.