Sound localisation is the process of determining the location of a particular source of sound, and this is achieved through the use of binaural and monaural cues. To investigate what factors affect the ability to localise sound, one hundred and eighty six psychology students underwent an experiment where subjects indicated what direction they heard a set of keys coming from when the keys were shaken above the participant’s head on three different positions of the midline. The four conditions in this study included head movement, no head movement, normal pinnae and distorted pinnae. As hypothesised, sound localisation improved significantly when the head was mobilized rather than immobilised, in conjunction to the pinnae being normal rather than distorted. These findings suggest that sound localisation is most successful when the head is mobile and the pinnae is normal.
The Effects of Pinnae and Head Movement in Sound Localisation The brain is equipped with the ability to perceive hearing, meaning it is able to recognise differences in intensity, spectrum and timing in order to correctly detect auditory stimuli. It is important to be able to locate sounds in the space surrounding us, and this is achieved through using the pinnae and head movement. Pinnae effects and head movement assist in directional auditory localisation (Muller, B.S., & Bovet, P. 1999) and spatial hearing (Denise Van Barneveld, Floor Binkhorst, A. John Van Opstal 2011). The pinnae is the outer structure of the ear which catches and guides sounds into the inner ear, and this study will assess the differences of sound localisation if the pinnae is distorted and undistorted. The use of head movement in this study is to investigate whether sound localisation improves when the head is mobilized or immobilised. The role in sound localisation is to detect the direction of the auditory stimuli coming from in front, behind, above or below the head (Martijn J H Agterberg; Myrthe K S Hol; Ad F M Snik; Marc van Wanrooij; A John Van Opstal), and this is done through the use of different cues, including binaural and monaural cues (Marc. M. Van. Wanrooij, A. John Van Opsal (2006). Binaural cues use interaural time difference (ITD) and interaural intensity difference (IID). ITD refers to the length of time that it takes for a noise to reach both ears, for example, if a noise originates from one particular side of the head, the noise will take longer to reach the opposite ear. This determines what direction sound is coming from. IID refers to the intensity of the auditory stimuli that is being heard, and this will help determine what direction the sound is coming from, similar to ITD. These compare sound on both ears through the recognition of sound pressure and time difference (Denise Van Barneveld, Floor Binkhorst, A. John Van Opstal 2011). Monaural cues are different to binaural cues as they only use one ear rather than both to localise sound. This study was based on Muller and Bovet’s article Role of Pinnae and Head Movements in Localising Pure Tones (1999), which investigated the role of the pinnae and head movement in sound localisation, as well as sound frequency. In their study, they discovered that head movement as well as normal pinnae and low frequency tones resulted in improved sound localisation. The study that the psychology students underwent did not include frequency tones to make matters simpler and to truly understand the function of pinnae and head movements in the role of sound localisation. To hypothesize, the accuracy of sound localisation will be greater when the pinnae is not distorted rather when the pinnae is distorted, and it is further hypothesized that the accuracy of sound localisation will be greater when the head is mobilised rather than immobilised. There are two independent variables in this study, and they each have two stages. These stages are normal pinnae and head immobilization, normal pinnae and head...
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