Physics
Structure of the Ear
The structure of the ear consists of three main parts: the outer ear, middle ear, and inner ear. Sound waves enter the outer ear and travel through the ear canal to the eardrum, causing it to vibrate. These vibrations are then transmitted through the middle ear bones to the cochlea in the inner ear, where they are converted into electrical signals and sent to the brain.
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eBook - PDFPhysics of the Body
Revised 2nd Edition
- John R. Cameron, James G. Skofronick, Roderick M. Grant(Authors)
- 2017(Publication Date)
- Medical Physics Publishing(Publisher)
The inner ear, along with the additional attachment of the vestibular (balance) sensors, is called the membranous labyrinth. 245 Physics of the Ear and Hearing malfunction. While they all involve physics, we know much more about the physics of the mechanical system than about the physics of the other parts. In this chapter, we deal with the sense of hearing only up to the auditory nerve. 11.1 The Ear and Hearing The ear is a cleverly designed converter of very weak mechanical sound waves in air into electrical pulses in the auditory nerve. Figure 11.1 shows most of the structures of the ear that are involved with hearing. The ear is usually divided into three areas: the outer ear, the middle ear, and the inner ear. What we com- monly call the ear (the appendage we use to help hold up our glasses) has no essential role in hearing. The outer ear consists of the ear canal, which terminates at the eardrum (tympanic membrane). The middle ear includes the three small bones (ossicles) and an opening to the mouth (Eustachian tube). The inner ear consists of the fluid-filled, spiral-shaped cochlea containing the organ of Corti. Hair cells in the organ of Corti convert vibrations of sound waves hitting the eardrum into nerve pulses that inform the auditory cortex of our brain of these sound waves. The inner ear is part of the labyrinth which also includes the sensors of the vestibular (sense of balance) system. The latter provides the brain with electrical signals that contain positional information of the head with respect to the direction of gravity and angular and linear motion information (see Section 11.10). One of the first medical physicists to study the physics of the ear and hearing was Hermann von Helmholtz (1821–1894). He developed the first modern the- ory of how the ear works. His work was expanded and extended by Georg Von Bekesey (1900–1970), a communications engineer who became interested in the function of the ear as part of the communication system.
eBook - PDF- Stanley A. Gelfand, Lauren Calandruccio(Authors)
- 2022(Publication Date)
- Thieme(Publisher)
2 Anatomy and Physiology of the Auditory System ▪ General Overview Hearing and its disorders are intimately inter- twined with the anatomy and physiology of the auditory system, which is composed of the ear and its associated neurological pathways. The auditory system is fascinating, but learning about it for the first time means that we must face many new terms, relationships, and concepts. For this reason it is best to begin with a general bird’s-eye view of how the ear is set up and how a sound is converted from vibrations in the air to a signal that can be interpreted by the brain. A set of self-explanatory drawings illustrating commonly used anatomical orientations and directions is provided in Fig. 2.1 for ready reference. The major parts of the ear are shown in Fig. 2.3. One cannot help but notice that the externally visi- ble auricle, or pinna, and the ear canal (external auditory meatus) ending at the eardrum (tympanic membrane) make up only a small part of the overall auditory system. This system is divided into several main sections: The outer ear includes the pinna and ear canal. The air-filled cavity behind the eardrum is called the middle ear, also known as the tympanic cavity. Fig. 2.2 shows how the structures of the hearing system are oriented within the head. Notice that the middle ear connects to the pharynx by the Eustachian tube. Medial to the middle ear is the inner ear. Three tiny bones (malleus, incus, and stapes), known as the ossicular chain, act as a bridge from the eardrum to the oval window, which is the entrance to the inner ear (Fig. 2.3). The inner ear contains the sensory organs of hearing and balance. Our main interest is with the structures and functions of the hearing mecha- nism. Structurally, the inner ear is composed of the vestibule, which lies on the medial side of the oval window; the snail-shaped cochlea anteriorly; and the three semicircular canals posteriorly.
eBook - PDF- Stanley A. Gelfand(Author)
- 2011(Publication Date)
- Thieme(Publisher)
Chapter 2 Anatomy and Physiology of the Auditory System General Overview Hearing and its disorders are intimately inter-twined with the anatomy and physiology of the auditory system, which is composed of the ear and its associated neurological pathways. The auditory system is fascinating, but learning about it for the first time means that we must face many new terms, relationships, and con-cepts. For this reason it is best to begin with a general bird’s-eye view of how the ear is set up, and how a sound is converted from vibrations in the air to a signal that can be interpreted by the brain. A set of self-explanatory drawings illus-trating commonly used anatomical orientations and directions is provided in Fig. 2.1 for ready reference. Figure 2.2 shows how the structures of the hearing system are oriented within the head. The major parts of the ear are shown in Fig. 2.3 . One cannot help but notice that the externally visible auricle, or pinna, and the ear canal (ex-ternal auditory meatus) ending at the eardrum (tympanic membrane) make up only a small part of the overall auditory system. This system is divided into several main sections: The outer ear includes the auricle and ear canal. The air-filled cavity behind the eardrum is called the middle ear , also known as the tympanic cavity. Notice that the middle ear connects to the phar-ynx by the eustachian tube. Medial to the middle ear is the inner ear. Three tiny bones (malleus, incus, and stapes), known as the ossicular chain, act as a bridge from the eardrum to the oval window, which is the entrance to the inner ear. H17004 The inner ear contains the sensory organs of hearing and balance. Our main interest is with the structures and functions of the hearing mechanism. Structurally, the inner ear is com-posed of the vestibule, which lies on the me-dial side of the oval window, the snail-shaped cochlea anteriorly and the three semicircular canals posteriorly.
eBook - ePubCommunication Acoustics
An Introduction to Speech, Audio and Psychoacoustics
- Ville Pulkki, Matti Karjalainen(Authors)
- 2015(Publication Date)
- Wiley(Publisher)
anatomical structure of hearing is also somewhat interesting, though not very important as such, except in some special cases, such as audiology or spatial hearing. Thus, a brief introduction to both the anatomy and physiology of the auditory system is considered sufficient in this chapter.7.1 Global Structure of the Ear
Humans, as well as most animals, have two sensors for sound – the left and right ear – and a complex neural system to analyse the sound signals received by them. The ear, more specifically the peripheral auditory system, consists of the external ear for capturing sound waves travelling in the air, the middle ear for mechanical conduction of the vibrations, and the inner ear for mechanical-to-neural transduction. Neural signals from the periphery are transmitted through the auditory pathway, where the neural signals are processed by different nuclei up to the auditory cortex where high-level analysis occurs.Figure 7.1 depicts a cross-section of one ear, including the external (outer), the middle ear, and part of the inner ear. Figure 7.2 shows a more schematic diagram characterizing the most essential parts of the system and the path from acoustic wave to neural signal.Cross-sectional diagram of one ear, showing the external, middle, and inner ear.Figure 7.1A simplified diagram of the ear.Figure 7.27.2 External Ear
The external ear (outer ear) consists of the pinna with the concha, the ear canal or meatus, and the eardrum or tympanic membrane as a borderline with the middle ear (Figure 7.1 ). The external ear is passive and linear, and its functioning is entirely based on the laws of acousticPhysiology and Anatomy of Hearing wave propagation. Passivity means that the external ear does not generate sound energy or ‘react’ to the sound, it only carries sound waves properly to the eardrum and the middle ear.Acoustically, the entire head (and shoulders) makes part of the external ear. The distance between the two ears, located at opposite sides of the head, causes an arrival time difference of the sound wavefront that depends on the angle of incidence. A difference in sound level appears at high frequencies due to shadowing by the head to the side that is opposite to the sound source. These phenomena and related effects in spatial hearing are discussed in Chapter 12 . In the present chapter, we concentrate on monaural
eBook - PDF- Aage Moller(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
CHAPTER Anatomy and General Physiology of the Ear Introduction This chapter is concerned with the general function of the ear and the auditory system. The auditory system is divided into the ear and the ner-vous system; the ear may be divided into the outer, middle, and inner ear as shown in the cross-sectional drawing of the human ear in Figure 1.1. The location of the ear in the skull is shown in Figure 1.2, whereas Figure 1.3 gives a schematic diagram of the ear as a whole. The outer and middle ears constitute the sound-conducting part of the ear, which transmits sound from air to the fluid of the inner ear. Thus, sound led through the external auditory canal sets the tympanic membrane into vibration, and these vibrations are transferred to the inner ear via the three small bones of the middle ear when the vibrations of the footplate of the stapes set the fluid in the cochlea into vibratory motion. As discussed later in this chapter, the cochlea, and particularly the basilar membrane in the cochlea, plays an important role in analyzing the sound and converting it into a neural code. That code, after being modified in the different brain nuclei of the ascending auditory pathway, is transferred to the part of the cerebral cortex that receives auditory in-formation. These transformations have not been completely studied, but our knowledge to date indicates that the information in the sound that reaches our ears undergoes substantial transformations. These matters are considered in Chapter 2. 1 1 FIGURE 1.1. Cross-section of the human ear. (Brodel, 1946.) 2 External Ear and Head 3 FIGURE 1.2. Location of the ear in the skull. (Based on Melloni, 1957.) External Ear and Head The external ear consists of the auricle and the ear canal. The external ear is shown in a schematic drawing in Figure 1.4. The groove called the concha is acoustically the most important part of the outer ear, whereas the flange that surrounds the concha is of little importance. Together with
eBook - PDFHuman Information Processing
An Introduction to Psychology
- Peter H. Lindsay, Donald A. Norman(Authors)
- 2013(Publication Date)
- Academic Press(Publisher)
PREVIEW THE EAR THE PHYSICS OF SOUND The frequency of sound The intensity of sound DECIBELS THE MECHANICS OF THE EAR The inner ear Movements of the hasilar membrane The hair cells ELECTRICAL RESPONSES TO SOUND Tuning curves Temporal coding in neural responses Coding of intensity information REVIEW OF TERMS AND CONCEPTS Terms and concepts you should know The parts of the ear Sound SUGGESTED READINGS The auditory system 4 PREVIEW This is the first chapter of the set of two on the auditory system. The ear is a fascinating piece of machinery. It is composed of tiny bones and mem-branes, with spiral-shaped tubes filled with fluid. When sound waves arrive at the ear, they are directed down precisely shaped passageways through a complex series of membranes and bones, which transform the sound waves to pressure variations in a liquid-filled cavity. These pressure variations cause bulges in a membrane, and the bulges act on a set of hairs that run along the length of the membrane. Each hair is connected to a cell, and when the hair is bent, the cell sends a signal along the acoustic nerve into the brain. Thus, what we hear is determined by which hairs are bent. By comparison with the ear, all the other sensory systems are much simpler. In the eye, for example, the mechanical parts are fairly straight-forward, and all the complexity resides in the interactions of the nerve cells at the back of the eye, in the retina. With the ear, the neural con-nections in the ear itself are relatively simple, and all the complexity is put into the mechanical structures that transform sound waves into par-ticular patterns of bulges along the basilar membrane.
eBook - PDFOtolaryngology
Basic Science and Clinical Review
- Thomas R. Van De Water, Hinrich Staecker(Authors)
- 2011(Publication Date)
- Thieme(Publisher)
In our houses, classrooms, and conference rooms, sound pressure reverberates off the walls, floor, and ceiling, producing a significant increase in the sound pressures that reach a listener’s ears. THE EAR AS A COLLECTOR OF SOUND O VERVIEW The external and middle ear are known to have a signif-icant influence on the sensitivity of the human ear to specific sounds. Although it is true that the inner ear is the most important element in determining whether the ear is sensitive to a specific sound frequency and level, the inner ear will not be able to respond with any sensitivity to signals that are greatly attenuated by the middle and external ear. Furthermore, signals that are best collected by the external and middle ear generally correspond to the most sensitive frequencies of hearing in humans and other animals (Rosowski, 1991). This section of the chapter reviews some of the acoustic and mechanical mechanisms used by the external and middle ear to gather sound and conduct it to the inner ear. Again, this section is meant to be an overview rather than an exhaustive or detailed review of this topic.Those readers wishing more detailed descriptions should seek other sources (see suggested readings, Dallos, 1973; Rosowski, 1996; Zwislocki, 1975). THE EAR AS A COLLECTOR OF SOUND 265 T ABLE 21 -3 W AVELENGTHS AND ANATOMIC STRUCTURES WITH COMPARABLE DIMENSIONS Frequency Anatomical Structural (Hz) Wavelength Structure Dimensions 200 1.7 m Torso 0.5 m 2000 17 cm Head 10 cm 4000 8.5 cm Pinna ear 4 cm canal length 2.5 cm 20,000 1.7 cm Ear canal 0.8 cm diameter Tympanic membrane T HE E XTERNAL E AR The external ear, as well as the head and body, has a significant influence on the sounds that reach the middle ear. This acoustic function of the external ear can be described by a frequency and directionally dependent alteration in the sound pressure at the tympanic mem-brane when compared with the sound pressure in the free field, sometimes called the external-ear gain.
eBook - ePubPhonetics
Transcription, Production, Acoustics, and Perception
- Henning Reetz, Allard Jongman(Authors)
- 2011(Publication Date)
- Wiley-Blackwell(Publisher)
The observation that a given phoneme can be produced with different articulatory gestures suggests that, in addition to an articulatory description, auditory and perceptual descriptions of speech sounds are important as well. For example, vowels are produced with rather different tongue positions by individual speakers, and the production of “rounded” vowels (like [u]) does not necessarily require a lip gesture after all: just stand in front of a mirror and try to produce an [u] without pursing the lips. This suggests that auditory targets (for example, the distribution of energy in a spectrum) rather than articulatory targets (like the position of the tongue) play the major role in speech perception. In other words, although it is possible to describe speech sounds in articulatory terms, and although the existing articulatory categorizations are generally quite effective, it may be advantageous to use auditory or perceptual categories.The following sections describe basic knowledge about the ear and the hearing process. The hearing organ is composed of a series of structures: the external ear, middle ear, and internal ear. The internal ear contains relatively simple sensory cells, which are surrounded by a watery liquid. The neural impulses registered by the sensory cells are then analyzed by the brain.12.1 The External Ear
What is called the “ear” in everyday language is only a small part of the actual hearing organ. As represented in Figure 12.1 , the external ear consists of the visible auricle (pinna), the meatus (ear canal), and the tympanic membrane (ear drum).Figure 12.1 External, middle, and internal ear and their main structures.The auricle helps humans to determine the origin of a sound, in particular, whether it comes from in front of or behind the head. The presence of this information can be easily demonstrated by putting on headphones. Since headphones disable the localization function of the auricles, no information is available about the location of the sound source in relation to the head. The music therefore sounds as if it comes from somewhere “inside the head.”After passing the auricle, the sound wave arrives in the ear canal (meatus). This channel is covered on the inside with a thin layer of earwax (cerumen), a noxious and sticky substance to prevent the ear canal from drying out and to keep insects out. If the ear canal is blocked, for example, by earwax, hearing capacity is considerably reduced.
eBook - PDFPhonetics
Transcription, Production, Acoustics, and Perception
- Henning Reetz, Allard Jongman(Authors)
- 2020(Publication Date)
- Wiley-Blackwell(Publisher)
The observation that a given phoneme can be produced with different articula-tory gestures suggests that, in addition to an articulatory description, auditory and perceptual descriptions of speech sounds are important as well. For example, vowels are produced with rather different tongue positions by individual speak-ers, and the production of “rounded” vowels (like [u]) does not necessarily require a lip gesture after all: just stand in front of a mirror and try to produce an [u] without pursing the lips. This suggests that auditory targets (for example, the distribution of energy in a spectrum) rather than articulatory targets (like the position of the tongue) play the major role in speech perception. In other words, although it is possible to describe speech sounds in articulatory terms, and Physiology and Psychophysics of Hearing Physiology and Psychophysics of Hearing 257 although the existing articulatory categorizations are generally quite effective, it may be advantageous to use auditory or perceptual categories. The following sections describe basic knowledge about the ear and the hearing process. The hearing organ is composed of a series of structures: the external ear, middle ear, and internal ear. The internal ear contains relatively simple sensory cells, which are surrounded by a watery liquid. The neural impulses registered by the sensory cells are then analyzed by the brain. Hearing in a nutshell The mammalian hearing system consists of three parts: outer, middle, and inner ear . The outer ear with auricle (pinna) and meatus (ear canal), ending at the tympanic membrane (ear drum) , channels acoustic signals to the middle ear . There, three tiny ossicles, malleus (hammer) , incus (anvil) , and stapes (stirrup) increase the (sound) pressure level from the tympanic membrane to the oval window of the inner ear by a levering action of the ossicles and concentrating the sound energy from the tympanic membrane onto the smaller oval window.
eBook - ePubSound & Hearing
A Conceptual Introduction
- R. Duncan Luce(Author)
- 2013(Publication Date)
- Psychology Press(Publisher)
PART IIIProperties of the Ear
1. THE OUTER AND MIDDLE EARS
1.1 Structures
The ear is composed of three quite distinct parts called the outer, middle, and inner ears. The only part we can see is the outer ear. See Fig. III. 1 for a cross-section of the entire structure.The outer ear too can be partitioned into three parts:An incoming sound wave is channeled by the pinna and external auditory meatus and, to a degree, modified by them until it reaches the tympanic membrane. At that point the middle ear comes into play.Informal terms: Cup Ear Canal Ear Drum ↕ ↕ ↕ More technical: Pinna External Auditory Meatus Tympanic Membrane The middle ear consists of an air-filled cavity, roughly a sphere, formed by a bony structure (see Fig. III. 1 ). This cavity is connected to the oral cavity by the eustachian tube. Within the cavity are three linked bones called ossicles, which are suspended by means of ligaments attached to the bone forming the cavity. The first ossicle is attached to the tympanic membrane and the third to a membrane called the oval window that interfaces the middle and inner ears. Basically, the ossicles simply link the outer ear to inner ear. (Their roles in hearing become clear later.)The names of the ossicles and their linkage is as follows:FIG. III.1 A schematic cross-section showing the major anatomical components of the ear. From Human Information Processing: An Introduction to Psychology (p. 221) by P. H. Lindsay and D. A. Norman, 1972, New York: Academic Press. Copyright 1972 by New York: Academic Press. Reprinted by permission.Tympanic membrane → malleus (also called the hammer) → incus (also called the anvil) → stapes → oval window The part of the stapes attached to the oval window is called the footplate.In addition to the suspension ligaments, muscles are located in bony tubes that connect both the malleus and the stapes to the wall of the cavity. (These are not shown in the figure.) Their role is to protect the inner ear from sounds that are so loud they can cause damage. We describe that action more fully later (Section III. 1.2
eBook - PDF- Myles L. Pensak, Daniel I. Choo, Myles L. Pensak, Daniel I. Choo(Authors)
- 2014(Publication Date)
- Thieme(Publisher)
Complex sounds may be described in terms of spec-tra. The spectrum of a sound identifies the frequencies and the relative amplitudes of the various components of a sound. 2.3 Physiology of Hearing The anatomy of the auditory system is addressed in Chapter 1. This chapter traces the course of the auditory stimulus from its generator to the auditory cortex, as shown in ▶ Fig. 2.4. Although the many relay stations in the auditory system all contribute to signal processing in a unique way, we highlight those areas pertinent to the practicing otologist and to those interested in the complexity of this exciting and mysterious sensory system. The natural or usual manner by which humans detect sound is via an airborne or acoustic signal. Once the sound is gener-ated, it travels through the air in a disturbance called a sound wave. This sound is slightly modified by the body and head, specifically the head and shoulders, which a ff ect the frequen-cies below 1,500 Hz by shadowing and reflection. 3 The flange and concha of the pinna collect, amplify, and direct the sound wave to the tympanic membrane by the external auditory mea-tus. At the tympanic membrane, several transformations of the signal occur: (1) the acoustic signal becomes mechanoacous-tic; (2) it is faithfully reproduced; and (3) it is passed along to the ossicular chain, is amplified, or, under certain condi-tions, is attenuated. 2.4 Transmission and Natural Resonance of the External Ear Natural resonance refers to inherent anatomic and physiologi-cal properties of the external and middle ear that allow certain Fig. 2.3 Two tones that are 180 degrees out of phase; note that the starting points for the two waves are the same, creating a mirror image. Fig. 2.4 Block diagram of the auditory system. The sound leaves its generator and travels through the external, middle, and inner ear and travels to the auditory cortex.
eBook - PDF- Ernest Glen Wever, Merle Lawrence(Authors)
- 2015(Publication Date)
- Princeton University Press(Publisher)
P A R T I I The Middle Ear as a Mechanical Transformer The Function of the Middle Ear OVER the long course of evolutionary history many things have happened to produce the highly efficient ear that is now possessed by man and his close relatives among the vertebrates. The original ear, as evolutionary study suggests, was present in some fore- runner of the fishes as a simple fluid-filled sac bearing on its in- terior walls a layer of sensory cells and including also, in contact with these cells and loading them, a dense and somewhat mobile mass. Doubtless the primary function of this organ was not hear- ,Otoliths Hair cells Hair cells Otoliths· B Fig. 19. A, the otolithic organ of a mollusc (Pecten inflexus), after Butschli. B, the saccule of man. ing at all but the determination of bodily position, for many ani- mals now living, including ourselves, have static organs of this nature, as for example the macular endings of the vestibule. It happened, however, for simple physical reasons, that this struc- ture was sensitive not only to bodily position but also to move- ments. It was sensitive to translatory movements of a sudden kind and to vibratory movements of slow rates. The same is true today of our own vestibular organs, which respond to jerky movements and also to sounds if these are of sufficient strength. Though as an auditory receptor this organ was dull as to sensi- tivity and limited to the very low frequencies, we can well imagine M I D D L E E A R A S M E C H A N I C A L T R A N S F O R M E R that it was of great biological value to its possessor. Therefore it was elaborated and improved through the evolutionary process until some of the fishes came to be equipped with an ear of credit- able sensitivity and range. This was an aquatic ear. It responded to vibrations passing through the water, and so it signaled events of the fish's immediate environment.
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