Sound waves, ears

The pioneering work on the chemical applications of ultrasound was conducted in the 1920 s by Richards and Loomis in their classic survey of the effects of high frequency sound waves on a variety of solutions, solids and pure liquidsQ). Ultrasonic waves are usually defined as those sound waves with a frequency of 20 kHz or higher. The human ear is most sensitive to frequencies in the 1-5 kHz range with upper and lower limits of 0.3 and 20 kHz, respectively. A brief but useful general treatment of the theory and applications of ultrasound has been given by Cracknel 1(2). 

Was this youT answer Your eyes are equipped to see only the narrow range of frequencies of electromagnetic radiation from about 700 trillion to 400 trillion hertz—the range of visible light. Radio waves are one type of electromagnetic radiation, but their frequency is much lower than what your eyes can detect. Thus, you can t see radio waves. Neither can you hear them. You can,however, turn on an electronic gizmo called a radio, which translates Tadio waves into signals that drive a speaker to produce sound waves your ears can hear. 

Ultrasound is the study and application of sound waves whose frequency is too high to be detected by the human ear, i.e., above about 16 kHz [1], This is a purely arbitrary cut-off point, determined by the limitations of the human ear. The physics describing the propagation of ultrasonic waves is the same as that describing the propagation of sound waves. 

The human ear is sensitive to sound waves with frequencies ranging from 50 Hz up to 15 kHz. Given that the velocity of sound in air is 343 m s l, what are the wavelengths corresponding to these frequencies ... 

It is possible that psi information flows directly from the psi receptor to the brain and then results in overt behavior. An everyday example of this would be your reaction if someone sneaks up behind you and makes a loud noise. You jump We would then talk about the reception and conversion of the sound waves into a barrage of neural impulses from the ear and their direct effect on various startle reflex mechanisms within the nervous system and brain, resulting in your behavior-jumping. The whole thing happens before consciousness has time to get involved. 

The ear is divided into three sections, these being the outer, middle, and inner ear. The outer ear consists of the pinna and ear canal. The sound wave enters the pinna and travels through the ear canal to the ear drum (tympanic membrane). The outer ear... 

Hearing works by the ear detecting sound waves, converting them into neural signals and then sending the signals to the brain. The ear has three divisions the external ear, the middle ear, and the inner ear (Figure 10). The external ear collects sound waves and funnels them down the ear canal, where they vibrate the eardrum. Within the middle ear, the eardrum is connected to... 

The threshold of hearing corresponds to a pressure variation of about 2 x 10 10 atm. Such a wave has a power density of 10-20 W m-2. The typical human ear responds comfortably to pressures up to a factor of 106 greater than this threshold at that point, pain is usually felt. The sound waves most young adults can hear have frequencies... 

If a wave persists only for a time At (or if we can only measure its frequency for a finite time At), the frequency is intrinsically unknown by an amount (1/4 At). For example, suppose we try to measure the frequency of a sound wave by using a microphone and an oscilloscope to count the number of cycles in one second. We could readily distinguish between a sound wave at 1000 Hz and one at 1001 Hertz, because the faster wave will go through one more cycle (in fact, your ear would hear a beat as the notes went in and out of phase with each other). It would be nearly impossible to distinguish between a wave at 1000 Hz and a wave at 1000.001 Hz at the end of one second, they would still be nearly perfectly in phase with each other. 

Sound waves are detected inside the cochlea of the inner ear. The cochlea is a fluid-filled, membranous sac that is coiled like a snail shell. The primary detection is accomplished hy specialized neurons inside the cochlea called hair cells (Figure 32.30). Each cochlea contains approximately 16,000 hair cells, and each hair cell contains a hexagonally shaped bundle of 20 to 300 hairlike projections called stereocilia (Figure 32.31). These stereocilia are graded in length across the bundle. Mechanical deflection of the hair bundle, as occurs when a sound wave arrives at the ear, creates a change in the membrane potential of the hair cell. 

The ear is nearly as complex as the eye and is also an outgrowth of the CNS. The ear converts sound waves into neural impulses which are transmitted to the brain for processing. Unlike the eye, toxins produce adverse effects only at limited sites in the ear. Like the eye, however, free entry of drugs into the inner ear is prevented by a selective filtering mechanism. 

Several tiny bones in the middle ear amplify and convert sound waves from the eardrum into fluid waves in the inner ear. There are no significant toxic exposures affecting the middle ear. 

Hearing in fish is processed in the inner ears, organs that receive input from vibrations created by sound. Fish do not have external ear canals like those in humans that connect the inner ear to the external environment. Sounds travel well in water and in fish s bodies, where they cause small bones in the inner ears to vibrate. The bones are denser than the rest of the animals tissues and therefore respond differently to sound waves. As the wavelengths of sounds vary, so do their effects on the small bones. These differences are registered by nerves and are interpreted as sound. 

Not all types of fish experience the same sensitivities to sound. One variable to sensitivity is the position of the swim bladder. The swim bladder is filled with gas, so its density is not the same as the density of the rest of a fish s body tissue. When sound waves strike the swim bladder, it vibrates, stimulating tissues that are connected to it. These vibrations aid the fish in interpreting sounds. Species that lack swim bladders are not as sensitive to sound as those who possess them. The fish that are most sensitive to sound are those whose swim bladders are directly connected to the middle ear. 

Sound waves are detected inside the cochlea of the inner ear. The cochlea is a fluid-filled, membranous sac that is coiled like a snail shell. The primary detection is accomplished by specialized neurons inside the cochlea called hair cells (Figure 32.30). Each cochlea contains... 

The human ear is sensitive to sound waves with frequencies in the range from a few hertz to almost 20 kHz. Auditory response is usually expressed in terms of the loudness level of a sound, which is a measure of the sound pressure. The reference level, which is given in the unit phon, is a pure tone of frequency 1000 Hz with sound pressure of 20 pPa (in cgs units, 210 dyn/cm ) loudness level is usually expressed in decibels (dB) relative to this reference level. If a normal observer perceives an arbitrary sound to... 

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