A method including: processing at a first processing frequency, such that each instance of processing is separated by a first processing time period, at least a first signal; increasing the processing frequency to a second processing frequency and switching from processing the first signal to processing a second signal; determining a parameter indicative of the quality of the second signal; and determining, within the first processing time period measured from the last instance of processing the first signal at the first frequency, which one or more signals to process at the next instance of processing by comparing respective parameters of at least the first and second signals.