Fig 14 shows a flatter response curve for Hero than Legend and Nexus One. Legend has the highest power in the low-frequency spectrum followed by Hero and Nexus One.
Also,the occurrence of peaks in the audio data due to external disturbance was seen only in Hero and Legend, where as it was eliminated in Nexus One by the hardware noise cancellation available on the phone. Thus, heart beats were more accurately detected using Legend or Hero than Nexus One.