What is Temporal Summation?

10 mins
02 May 2016


Temporal summation occurs when the human ear integrates energy over time, which stems from a continuous sound.



It is well established in the scientific literature (e.g. Zwislocki in the 1960s) that the absolute threshold of a sound depends on its duration. If the sound duration is longer than 500ms then absolute threshold is independent of sound duration, but below 500ms the threshold increases (and loudness decreases) as the duration gets less. This is especially apparent below 200ms and is the reason why most normal hearing people can listen to a click (broadband) at pretty high intensities (say 90 – 100 dB nHL) and not regard it as uncomfortably loud at all. The click is too short to integrate enough energy for the sound to become uncomfortably loud, even at high intensities. If the sound became continuous instead of transient then the click would essentially become a white noise, and then it might begin to feel uncomfortably loud pretty quickly…intensity is measured as energy per unit time. The ear integrates this energy over time, which is known as temporal summation. Perceptual threshold improves by about -3dB per doubling of duration up to 500ms according to the Zwislocki model, but that is an average value. It is very variable amongst individuals.


Michael Maslin
After working for several years as an audiologist in the UK, Michael completed his Ph.D. in 2010 at The University of Manchester. The topic was plasticity of the human binaural auditory system. He then completed a 3-year post-doctoral research program that built directly on the underpinning work carried out during his Ph.D. In 2015, Michael joined the Interacoustics Academy, offering training and education in audiological and vestibular diagnostics worldwide. Michael now works for the University of Canterbury in Christchurch, New Zealand, exploring his research interests which include electrophysiological measurement of the central auditory system, and the development of clinical protocols and clinical techniques applied in areas such as paediatric audiology and vestibular assessment and management.

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