According to examples, an apparatus may include a processor and a memory on which is stored machine readable instructions that are to cause the processor to determine a reference frame from a plurality of frames received at multiple different times, in which each of the plurality of frames includes audio signal data, and in which the reference frame includes audio signal data that identifies a highest audio signal level among audio signals identified in the plurality of frames. The reference frame may be time-aligned with each of the plurality of frames other than the reference frame to obtain respective time-aligned frames. The audio signals identified in each of the respective time-aligned frames may be added together to generate respective added audio signals. The respective added audio signals may be combined together to obtain a combined audio signal and the combined audio signal may be outputted.