A system configured to improve wakeword detection. The system may selectively rectify (e.g., attenuate) a portion of an audio signal based on energy statistics corresponding to a keyword (e.g., wakeword). For example, a device may perform echo cancellation to generate isolated audio data, may use the energy statistics to calculate signal quality metric values for a plurality of frequency bands of the isolated audio data, and may select a fixed number of frequency bands (e.g., 5-10%) associated with lowest signal quality metric values. To detect a specific keyword, the system determines a threshold λ(f) corresponding to an expected energy value at each frequency band. During runtime, the device determines signal quality metric values by subtracting residual music from the expected energy values. Thus, the device attenuates only a portion of the total number of frequency bands that include more energy than expected based on the energy statistics of the wakeword.