Mindblown: a blog about philosophy.
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Subjective Response
So far we have traced the sound signal down the ear canal to the eardrum, through the auditory ossicles, through the oval window to the cochlear fluid to the basilar membrane and the hair cells, and finally to the neural impulses sent to the brain. How does the brain interpret these signals? Our study now…
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Theories of Hearing
Pythagoras in the sixth century BCE was perhaps the first to recognize that sound is an airborne vibration [10]. Hippocrates in the fourth century BCE recognized that the air vibrations are picked up by the eardrum but thought that the vibrations were transmitted directly to the brain by bones. In 175 CE, Galen of Pergamum, a…
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Working of the Ear Mechanism
When a sound wave reaches the ear, it travels down the auditory canal until it reaches the eardrum. It sets the eardrum in motion and this vibration is transmitted across the 2 mm gap to the oval window by the lever system comprised of the auditory ossicles. It is thought that this mechanical system is an…
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Construction of the Ear
The fleshy appendage on the side of the head (the pinna) is not as well developed in humans as in some animals. Its function is to focus sound into the ear canal. It helps us to localize the source of sound, particularly in the vertical direction, and is more effective at higher frequencies. The ear…
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Construction of Ear and Its Working
The ear can be divided into three main parts (Figure 4.1): the outer, middle, and inner ear. The outer ear consisting of the fleshy pinna and ear canal conducts the sound waves onto the eardrum. The middle ear converts the sound waves into mechanical motion of the auditory ossicles, and the inner ear converts the mechanical motion into neural…
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Introduction
The human ear is a marvelous and very sensitive biomechanical system for detecting sound. If it were only slightly more sensitive, we would be able to hear the Brownian (random) motion of the air molecules and we would have a perpetual buzz in our ears! The ear has a wide frequency response from about 15…
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Acoustic Modeling Using Equivalent Circuits
Electrical analogies have often been found useful in the modeling of acoustical systems. There are two alternatives. The sound pressure can be represented by voltage and the volume velocity by current, or alternatively the sound pressure is replaced by current and the volume velocity by voltage. Use of electrical analogies is discussed in chapter 11 of…
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Numerical Approaches: Finite Elements and Boundary Elements
In cases where the geometry of the acoustical space is complicated and where the lumped‐element approach cannot be used, then it is necessary to use numerical approaches. In the late 1960s, with the advent of powerful computers, the acoustical finite element method (FEM) became feasible. In this approach, the fluid volume is divided into a number of…
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Other Approaches
3.19.1 Acoustical Lumped Elements When the wavelength of sound is large compared to physical dimensions of the acoustical system under consideration, then the lumped‐element approach is useful. In this approach it is assumed that the fluid mass, stiffness, and dissipation distributions can be “lumped” together to act at a point, significantly simplifying the analysis of…
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Waveguides
Waveguides can occur naturally where sound waves are channeled by reflections at boundaries and by refraction. Even the ocean can sometimes be considered to be an acoustic waveguide that is bounded above by the air–sea interface and below by the ocean bottom (see chapter 31 in the Handbook of Acoustics [1]). Similar channeling effects are also sometimes…
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