The “Cocktail Party” effect can be described as the ability to interpret sound coming from a single source while spectrally masked by background noise. Our brains utilise the binaural cues available to enhance the signal to noise ratio enabling us to understand what we wish to listen to. Binaural hearing is the mechanism developed in the auditory pathway during infancy which allows us to listen to speech masked in background noise.
To measure the level of binaural processing – psychoacoustic tests such as the Binaural Masking Level Difference (BMLD) are performed to determine thresholds. Two conditions are traditionally tested:
- Monaural condition (N0S0) – both ears received the same signal masked in spectrally similar noise.
- Binaural condition (N0Sπ) –there is a phase difference in the signal between the ears.
By introducing the phase difference between the ears, the brain has additional information about the signal. This enables the brain to distinguish between the signal and the noise at much lower thresholds. The auditory cortex is sensitive to interaural level and time differences which demonstrates the mechanism developed to enable us to distinguish sound in background noise.
The sensitivity to binaural cues is developed during infancy. The pathway has been shown in both human and animal studies to be impacted upon anatomically and physiologically due to auditory deprivation. Otitis media (OM) with effusion is a widespread auditory problem in childhood which causes auditory deprivation.
Persistent OM has been linked to behavioural problems in school classrooms which had been demonstrated through reduced BMLD thresholds. These reduced thresholds demonstrate the impact of OM on the auditory pathway and the problems stemming from limited binaural processing.
Charles Darwin University plays an active role in hearing research relating to binaural hearing with both undergraduates and postgraduates working in this field. Research in this field spans psychoacoustic measurements, instrumentation and data acquisition of electrical activity using non-invasive electroencephalography, to the time-frequency analysis of the auditory evoked potentials.
Research projects and possible PhD and Masters by Research may include:
- Investigate the presence of hearing in the auditory evoked response of the EEG of the brain.
- Analysis of EEG signals of the brain to detect binaural hearing disorders.
Research Coordinator: Prof Friso De Boer