A system configured to process an audio signal, the system comprising: one or more processors configured to execute computer program modules, the computer program modules comprising: a first set of one or more modules configured to transform individual time sample windows of the audio signal into the frequency-chirp domain, wherein the frequency-chirp domain representation of a given time sample window specifies a transform coefficient as a function of frequency and fractional chirp rate for the signal portion, wherein fractional chirp rate is chirp rate divided by frequency, a second set of one or more computer program modules configured to determine, from the obtained transformed audio information for the given time sample window, a pitch likelihood metric as a function of pitch and fractional chirp rate for the audio signal within the time sample window, and a third set of one or more computer program modules configured ( i) to divide the time sample windows into groups within processing time windows, ( ii) to identify a primary time sample window within a given processing time window, ( iii) to determine pitch for time sample windows within the given processing time window by iterating through the processing time window from the primary time sample window toward one or both of the boundaries of the processing time window and determining the estimated pitch and estimated fractional chirp rate for a given time sample window from values of pitch likelihood metric weighted based on parameters of sound determined for a time sample window adjacent to the given time sample window. one or more processors configured to execute computer program modules, the computer program modules comprising: a first set of one or more modules configured to transform individual time sample windows of the audio signal into the frequency-chirp domain, wherein the frequency-chirp domain representation of a given time sample window specifies a transform coefficient as a function of frequency and fractional chirp rate for the signal portion, wherein fractional chirp rate is chirp rate divided by frequency, a second set of one or more computer program modules configured to determine, from the obtained transformed audio information for the given time sample window, a pitch likelihood metric as a function of pitch and fractional chirp rate for the audio signal within the time sample window, and a third set of one or more computer program modules configured ( i) to divide the time sample windows into groups within processing time windows, ( ii) to identify a primary time sample window within a given processing time window, ( iii) to determine pitch for time sample windows within the given processing time window by iterating through the processing time window from the primary time sample window toward one or both of the boundaries of the processing time window and determining the estimated pitch and estimated fractional chirp rate for a given time sample window from values of pitch likelihood metric weighted based on parameters of sound determined for a time sample window adjacent to the given time sample window. a first set of one or more modules configured to transform individual time sample windows of the audio signal into the frequency-chirp domain, wherein the frequency-chirp domain representation of a given time sample window specifies a transform coefficient as a function of frequency and fractional chirp rate for the signal portion, wherein fractional chirp rate is chirp rate divided by frequency, a second set of one or more computer program modules configured to determine, from the obtained transformed audio information for the given time sample window, a pitch likelihood metric as a function of pitch and fractional chirp rate for the audio signal within the time sample window, and a third set of one or more computer program modules configured ( i) to divide the time sample windows into groups within processing time windows, ( ii) to identify a primary time sample window within a given processing time window, ( iii) to determine pitch for time sample windows within the given processing time window by iterating through the processing time window from the primary time sample window toward one or both of the boundaries of the processing time window and determining the estimated pitch and estimated fractional chirp rate for a given time sample window from values of pitch likelihood metric weighted based on parameters of sound determined for a time sample window adjacent to the given time sample window.