While patients with brain stem implants processed the loudness of all pitches the same, patients with cochlear implants processed the loudness of low pitches differently. Dr. Zeng cautioned that more work is needed. The investigators in this study only tested simple tones. How the brain processes the loudness of complex sounds, such as speech, that consist of many tones, needs to be examined. In addition, loudness is only one feature of sound.
Similar work needs to continue on how the brain processes other aspects of sound such as pitch.