![Production of sound
► Sound is a form of energy
► The vibration of an elastic body (tuning fork, piano string, vocal cords) gives rise to
the propagation of pressure waves [ a sequence of increases (compressions)
and decreases (rarefactions) in pressure].
►When the vibrating object is a sound source, these pressure waves are known as
sound waves.
►Sound wave:
Energy transmission by media
Longitudinal wave = pressure wave
縱波: 波傳遞時，介質振動的方向與波行進方向平行
橫波:波傳遞時，介質振動的方向與傳遞方向互相垂直](https://image.slidesharecdn.com/03042012-2-120306085937-phpapp02/85/03042012-2-42-320.jpg)
台科大 助聽器到電子耳 03042012 2
- 1. 聽能障礙與輔具的應用— 從助聽器到電子耳 王智弘 醫師 三軍總醫院 耳鼻喉頭頸外科部 Chih-Hung Wang, MD, PhD Department of Otolaryngology-Head and Neck Surgery Tri-Service General Hospital, National Defense Medical Center Taipei, TAIWAN, ROC
- 2. Auditory System = Energy Transformation System acoustic energy---mechanical energy---hydraulic energy---bio-electric energy → Outer ear ←→ Middle ear ←→ Inner ear ←
- 3. How Do We Hear?
- 4. Sound waves
- 5. ++++ +++ ++++ +++
- 6. Anatomy of the Outer Ear The Outer Ear: Auricle (pinna): is composed of a sheet of cartilage, and this is continous with the cartilage which forms the framework of the outer 1/3 of the EAC. Function: ☆ It protects the ear canal and eardrum by repelling any objects that strike it ☆ collect and capture the acoustic energy and direct it to the tympanic membrane ☆ the surface of the auricle can modify the spectral composition of the incoming sound ☆ localize the source of sound, using intensity and phase differences of signal at two ears ☆ beautiful to look at
- 7. Anatomy of the Ext. Ear Canal External auditory canal: A narrow, slightly tortuous passage (from concha to the tympanic membrane, approximately 2.5~3 cm in the adult). The membrane is set obliquely in the depth of the canal, in such a way that the front (anterior) wall is longer than the back (posterior) wall. (inferior wall of EAC is longer than superior one) . sup. pos. ant. inf. 5 mm ant. sup inf. pos
- 8. The ear canal reinforces sound Sound is directed towards the eardrum in two ways: ► Intensity of sound at eardrum is increased by 20 dB because of resonances from the external ear (concha, meatus, canal and eardrum) ► This increase in sound intensity is for high frequency sounds. In adults the peak freqeuncies are found around 2500 Hz. For children the peak intensities are at higher frequencies
- 9. Resonance
- 10. 耳道的共振效應 波長: 4 x L (管長) 基礎共振頻率 first harmonic 4 x L x 1/3 第三共振頻率 third harmonic 4 x L x 1/5 第五共振頻率 third harmonic
- 11. Function of Ext. Ear Canal In the adult, the outer cartilaginous portion of the canal runs slightly upwards and backwards, the inner bony portion running slightly downwards and forwards. The skin covering the cartilaginous portion of the canal contains short hairs, ceruminous and sebaceous glands. Two constrictions in the canal: one at the junction of the cartilaginous and bony portions; the other, the isthmus, 5 mm from the tympanic membrane, in the bony portion. Function: cartilage bone ☆Cleaning: cilia Outer 1/3 Inner 2/3 ☆Protection: cerumen, moisture ☆Resonance & sound amplification: Hair Yes NO Natural frequency in EAC: Sebaceous gland Yes NO 343m/(4x0.03) = 2834 HZ Ceruminous gland Yes NO 2500~4000 Hz, 2x~4x intensity Sweat gland Yes NO ☆Sound localization:
- 12. The Eardrum & The Ossicles
- 13. The Middle ear as an Impedence Transformer ☆ The middle ear acts as an impedence-matching device. ☆ Amplify sound pressure: @ Lever action: d1p1=d2p2 malleal arm: incudal arm = 1.3: 1 @ Areal ratio of the tympanic membrane to the oval window a1p1=a2p2 tympanic memb.: oval window = 14: 1 → x 18.2 → 25.25 db SPL Exp.: Resonance in EAC: 2.5K~4k Hz: 2x ~ 4x
- 14. The Middle Ear Cleft: The tympanic cavity is an air-containing cavity in the air- petrous part of the temporal bone and is lined with mucous membrane. It contains the auditory ossicles, and communicates in ossicles, front through the E- E- tube with the nasopharynx and behind with the mastoid antrum. antrum. Roof: A thin plate of bone, the tegmen tympani, which is part of the petrous temporal bone It seprates the tympanic cavity from the meninges and temporal lobe of the brain in the middle cranial fossa. fossa. Floor: A thin plate of bone, which may be deficient and partly replaced by fibrous tissue. It separates the tympanic cavity from the superior bulb of the internal jugular vein.
- 15. Schematic diagram of the middle ear E-tube : 17-18 mm long at birth; 35 mm in adult
- 16. Structure of Inner Ear
- 17. Anatomical two parts: 1). Bony labyrinth: comprising a series of cavities within the bone labyrinth 2). Membranous labyrinth: comprising a series of membranous sacs and ducts contained within the bony labyrinth.
- 18. Anatomy of the Labyrinth Bony Labyrinth: Vestibule: The central part of the bony labyrinth, lies posterior to the cochlea and ant. to the semicircular canals. Within the vestibule are the saccule and utricle of the membranous labyrinth. Semicircular canals: Within the canals are the semicircular ducts. Each canal has a swelling at one end called ampulla. ampulla. Cochlea: Two and a half turns in the human, these coils(holly bony tube) turning around a central ‘pillar’, the pillar’ modiolus
- 23. Membranous Labyrinth: Utricle: indirectly connected to the saccule by utricular duct. Saccule: globular in shape, saccular duct Semicircular ducts: Cochlear duct: triangular in cross section, connected to the saccule by the ductus reunions.
- 24. Perilymph: • Primarily formed by filtration from blood vessels in the inner e ar • Communicates with the cerebrospinal fluid (CSF) through the coch lear aqueduct, a narrow channel 3- 4 mm long, with its inner ear opening at the base of the scala tympani. • Resembles the extracellular fluids: ( high Na+ :140 mEq/liter; low K+:10 mEq/liter; Protein: 200-400 mg%, CSF: Na+ :152 mEq/liter; K+:4 mEq/liter; Protein: 20-50 mg% ) Endolymph: • Produced by the secretory cells in the stria vascularis of the cochlea and the dark cells of the vestibular labyrinth. • Re-absorption of endolymph take place in the endolymphatic sac. • Resenble the intracellular fluids: ( low Na+ :5 mEq/liter; high K+:144 mEq/liter; Protein: 126 mg%)
- 25. Chemical Composition of the Cochlear fluids
- 26. Blood supply of the inner ear Basilar artery—ant. inf. cerebellar artery—labyrinthine artery ↗ common cochlear a. --↗main cochlear a ----------------------------- ↓ ↘vestibulo-cochlear a ↗cochlear ramus ↑ →post. vestibular a.↓ ↘ ant. vestibular a. ----------------------------------------------------------↑
- 27. Blood supply of the inner ear Basilar artery—ant. inf. cerebellar artery—labyrinthine artery ↗ common cochlear a. --↗main cochlear a ----------------------------- ↓ ↘vestibulo-cochlear a ↗cochlear ramus ↑ →post. vestibular a.↓ ↘ ant. vestibular a. ----------------------------------------------------------↑
- 32. Shearing is a particular form of bending
- 33. Inner Hair Cell Outer Hair Cell
- 34. Innervation and central connections Two types: Afferent fibres: carrying sensory fibres: information to the brain. Efferent fibres: Pass from the brain-stem to fibres: brain- the cochlea, perhaps 1000 in number As many as 95% of all afferent fibres make contact with the inner hair-cells, 5% with hair- outer hair cells, and each inner hair-cell has hair- terminals from about 10~20 afferent fibres. fibres. The vast majority of the fibres of the cochlear nerve (about 30,000 of them) are afferent and their cell bodies are in the spiral ganglion in the modiolus. modiolus. The modiouls contains many small canal, the most central of them carrying fibres from the apex of the cochlea, while the outermost canal carry fibres from the basal part of the cochlea.
- 36. Travelling wave:
- 37. Travelling wave:
- 38. Response to a 150 Hz tone Response to a pulse sequence Response to a 1.5 kHz tone Low frequency traveling wave in 3-D Response to a 15 kHz tone High frequency traveling wave in 3-D
- 39. Tuning Curve The frequency sensitivity of a hair cell can be displayed as a tuning curve
- 40. PHYSICAL PROPERTIES OF SOUND Chih-Hung Wang, MD, PhD Tri-Service General Hospital, National Defense Medical Center 王智弘 三軍總醫院耳鼻喉部 國防醫學院耳鼻喉學系
- 41. Nature of sound • The sensation of sound is determined by the interaction of sound waves with the hearing system. • The normal human ear has an auditory sensitivity which ranges from 20-20,000 Hz. Humans: 20- 20,000 Hz Whales: 20- 100,000 Hz Bats: 1500- 100,000 Hz Frogs: 600- 3000 Hz Fish: 20- 3000 Hz Crickets: 500- 5000 Hz
- 42. Production of sound ► Sound is a form of energy ► The vibration of an elastic body (tuning fork, piano string, vocal cords) gives rise to the propagation of pressure waves [ a sequence of increases (compressions) and decreases (rarefactions) in pressure]. ►When the vibrating object is a sound source, these pressure waves are known as sound waves. ►Sound wave: Energy transmission by media Longitudinal wave = pressure wave 縱波: 波傳遞時，介質振動的方向與波行進方向平行 橫波:波傳遞時，介質振動的方向與傳遞方向互相垂直
- 43. At rest Compression Rarefaction
- 44. Characters of sound 1). Frequency: one double vibration is called a cycle. The frequency of sound is determined by the number of complete cycles per second and is expressed in hertz (Hz). ► Pitch: Psychoacoustics terms ► Octave: at twice the frequency: ► Fundamental frequency: the basic underlying sine wave ► Harmonics: the higher frequencies based on multiples of a fundamental frequency.
- 46. •The lowest component of the waveform is known as the FUNDAMENTAL •The second harmonic is twice the fundamental frequency, the third harmonic is three times the fundamental frequency, and so forth.
- 47. 2). Period: the time for one double vibration= second/ per cycle 3). Wave length: the distance for one cycle = m/sec 4). Phase: the phase of a sine wave corresponds to its distance form zero at the moment in which the vibration begins (onset) and is usually defined in terms of time (period) or angular measure.
- 48. interference If you strike a tuning fork and rotate it next to your ear, you will note that the sound alternates between loud and soft as you rotate through the angles where the interference is constructive and destructive.
- 49. The arrow indicates one cycle of the sound. The time it takes to complete a cycle is the period. Frequency is the inverse of this, the number of cycles in a second. The distance sound travels during one period is the wavelength. P = 1/f λ = S/f The upside down y is λ (lambda): wavelength P = period, f = frequency S = the speed of sound 20℃、海平面上，聲音的速率: 343 m/s 溫度的變化:『v = (331 + 0.6T) m/s 』 在水中，20℃時聲音的速率: 1,482 m/s 鋼鐵材質中則大約5,960 m/s。
- 50. Sine wave • The waveform produced by simple harmonic motion is the SINE WAVE • the simplest type of sound wave is one which has only one frequency and is constant in amplitude
- 51. Beats When two waves with the same amplitude but different frequency are added together a phenomenon called "beating" occurs.
- 52. Refraction 折射 ▶In the first, the beam crosses the boundry between warm and cool at a right angle. All that happens is the wavelength changes. It gets shorter, since the speed of sound is lower in the cool air. ▶ Look at the beam that strikes the boundry at an angle.The wavefront that has just crossed actually has two wavelengths; long for the part still in the warm air, short for the part in the cold.This makes it skewed. All later waves just propagate off this crooked wavefront, in a new direction.
- 53. Resonance
- 54. 5). Amplitude: The difference between normal (atmospheric) pressure and the pressure in the presence of a sound wave. It varies with time between positive and negative values and is expressed in pascals (newtons/m2). The lower limit to the hearing threshold at 1k Hz: 2 x 10-5 newton/m2= 20 µPa ► The measurement of amplitude of the sound wave: Pressure: Newton/m2 or dyne/cm2 Intensity: power : watt/m2 or watt/cm2 Exp: 1k Hz: (power) 1 x10-16 watt/cm2 =(pressure) 0.0002 dyne/cm2 or 2 x 10-4 dyne/cm2 Intensity being proportional to the square of the amplitude of sound pressure (I ∞ P2)
- 55. Pascal
- 56. Amplitude and waveform •Amplitude of sounds as loudness. •The shape of a sound is its waveform •The shape of the curve is very important in establishing the timbre of the sound..
- 57. Tuninig curve of single nerve fiber 100 dB 80 60 40 20 1 10 40 kHz Normal Loss of OHC Loss of IHC & OHC
- 58. sound_zh_TW.jar
- 59. Measurement of Sound MKS CGS Length m cm Mass Kg g Time second second sound wave pressure Newton/m2 dyne/cm2 intensity watt/m2 watt/cm2 F=ma Newton: 1N = 105 dyne
- 60. Bel system Bel system=Intensity (power) system, named after the scientist Alexander Graham Bell BelIL = log I/I0 0 bel =1 x 10-12 watt/m2 (I0: a tone which is only just audible= a threshold sound) 1 bel =10 x 10-12 watt/m2 3 bel =10 x 10 x 10 x 10-12 watt/m2 (a whisper is 1000 times more powerful than a threshold sound = raised to the power of three)
- 61. Decibel system Decibel system: for clinical purposes, the bel has been broken down into ten smaller units known as decibels (dB) dBeL = 10 log I/I0 I: the intensity to be measured I0: threshold sound = 1 x 10-12 watt/m2 = 1 x 10-16 watt/cm2 Exp: when noise is 1 x 10-14 watt/cm2 dBeL= 10 log 1 x 10-14 watt/cm2 / 1 x 10-16 watt/cm2 =20 dB Similarly, a whisper (3 bels) = 30 dB = 103 x threshold sound A conversational voice (6 bels) = 60 dB = 106 x threshold sound A loud shout (9 bels) = 90 dB = 109 x threshold sound Loudness: Psychoacoustics terms
- 62. (I (power)∞ p2 ) Intensity being proportional to the square of the amplitude of sound pressure dBSPL = 20 log P/P0 P=power Exp.: A: 0.002 dyne/cm2: dBSPL=20 log 0.002/0.0002= 20 B: 0.02 dyne/cm2: = 40 C: 0.004 dyne/cm2: = 26 BelIL = dBelIL/10 = dBSPL/20
- 63. Auditory threshold • 1). dB SPL (sound pressure level): a value in decibels which express the pressure of sound in relation to a reference pressure which for conventional purposes is the minimum pressure required for the perception of a 1000-4000 Hz sine wave in the average adult. • 2). dB HL (hearing level): the minimum intensity at which a person can hear at a specific frequency (e.g. 1000 Hz ) in relation to a basic value (0 dB HL) which represents minimum hearing in normal hearing subjects. • 3). dB SL (sensation level): the level of hearing in dB HL above threshold for the subject being tested.