Non-linear Distortion against Hearing Loss

Sa？etak Today, an increasing problem is hearing loss caused by increasingly high Sound Pressure Levels (SPL). Extremely loud noises and sounds originating from our environment often cause damage to our ears and result in noise-induced hearing loss (NIHL). There are procedures to increase loudness without increasing the physical, measurable Sound Pressure Level (SPL). Procedures using equal loudness sensitivity curves amplify at different frequencies. It was our intention to create a device that will control volume and clarity to a suitable level without inflicting any damage to the ear since the sound pressure level remains at a lower level. Additionally, our aim was to design a device, that, in contrast with current procedures today, does not weaken or masquerade the sound, does not distort the intricacies of music or alter tonality. Environmental conscious thinking, especially in energy saving, has become increasingly important today. When amplifying sound, we can achieve significant energy savings from utilising a lower Sound Pressure Level (SPL). Our patented method imitates the human ear’s distortion and non-linear behaviour. Any non-linear distorting causes a sense of loudness growth, but the modified sound will become realistic if we come closer to the human ear’s distortion. In our investigations, we conclude that, by setting (or "imitating") an overtone range similar to the human ear’s distortion, we can achieve an increase in loudness in the entire audible frequency spectrum without loss of sound quality. Our prototype was constructed with the ability to carry out a subjective comparative loudness test. The data was collected individually by questionnaire, and later calculated using the arithmetical mean of the answers, with the results given in decibels. An average increment of 2.7 dB was measured electronically based on the 66 completed questionnaires used with the Triode Proof of Concept Model. The results demonstrated that an increase of loudness level can be achieved not only with the currently used Fletcher-Munson curves, but with the help of the procedure found in our study. In the implementation of this unique method, an increase in the sound pressure level can be avoided, and, so, without SPL increases, the subjective loudness of the sound can be increased, ensuring the ear will not be exposed to the adverse consequences of the higher sound pressure level. Our unique equipment and methodology can help reduce hearing damage without the discomfort caused by coloured tones. While further studies and improvements are required, the