Dichotic pitch

When continuous white noise (with a frequency content below about 2000 Hz) is presented by headphones to the left and right ear of a listener, and given a particular interaural phase relationship between the left and right ear signals, a sensation of pitch (psychophysics) may be observed. Thus, stimulation of either ear alone gives rise to the sensation of white noise only, but stimulation of both ears together produces pitch. Therefore, as a special case of dichotic listening, such a pitch is called dichotic pitch or binaural pitch. Generally, a dichotic pitch is perceived somewhere in the head amidst the noisy sound filling the binaural space. To be more specific, the dichotic pitch is characterized by three perceptual properties: pitch value, timbre, and in-head position (lateralization). Experiments on dichotic pitch were motivated in the context of the study of pitch in general, and of the binaural system in particular, relevant for sound localization and separation of competing sound sources (see cocktail party effect). In the past, various configurations of dichotic pitch were studied and several auditory models were developed. The great challenge for psychophysical and physiological acoustics is to predict both the pitch value and pitch-image position in one model. For more information, references, audio demos etc. see more.

Studies

There have been many findings on the subject of dichotic pitch, showing that different disorders experience it in multiple different ways. Individuals who suffer from dyslexia seem to experience dichotic pitch in a similar way, too if they were trying to distinguish words and letters. Robert F. Dougherty and team, ran an experiment using both dyslexic and non-dyslexic children. The participants were given a melody to listen to and different tones were then played within the melody. The dyslexic children were able to decipher the higher pitched tones but were unable to distinguish the lower notes from the background melody. It became apart that the lower caused some sort of auditory and sensory problem for the dyslexic children that made it harder for their brain to sort out the information being sent to it.

A study done by Bianca Pinheiro Lanzetta-Valdo and team looked at children with the diagnosis of Attention Deficit Hyperactivity Disorder (ADHD) and dichotic pitch. At the beginning of the experiment, all of the children were at a base level of the medication methylphenidate, a stimulant that is used to try and calm individuals with ADHD. Over a 6-month period, the children were given auditory stimulation that consisted of white noise, and during this stimulation, they would be given physical, neurological, visual and auditory examination, as well as biochemical tests to see if any improvement was made. Lanzetta-Valdo and collaborators did find improvement in these participants over the 6 months in their different evaluations, but there are controversy results on this topic.

References

Dougherty, R.F., Cyander, M.S., Bjornson, B.H., Edgell, D., & Giaschi, D.E. (1998). Dichotic Pitch: A new stimulus distinguishes normal and dyslexic auditory function. NeruoReport.9(13)Retrieved from https://www.researchgate.net/profile/Robert_Dougherty/publication/13482828_Dichotic_pitch_A_new_stimulus_distinguishes_normal_and_dyslexic_auditory_function/links/00b4952dafbd0e7c3d000000/Dichotic-pitch-A-new-stimulus-distinguishes-normal-and-dyslexic-auditory-function.pdf Lanzetta-Valdo, B. P., de Oliveira, G. A., Ferreira, J. C., & Palacios, E. N. (2017). Auditory Processing Assessment in Children with Attention Deficit Hyperactivity Disorder: An Open Study Examining Methylphenidate Effects. International Archives Of Otorhinolaryngology, 21(1), 72-78. doi:10.1055/s-0036-1572526