Lecture 4, Biophysics, HUE AHST, 2024

BIOPHYSICS FIRST LEVEL 2024-2025 Prepared By Dr. Nermin Ali Dr. Enas Lotfy Lec No. 1 Course Code: FAC-104 1 Page 1  CHAPTER 3 SOUND AND ULTRASOUND THERAPY...

BIOPHYSICS FIRST LEVEL 2024-2025 Prepared By Dr. Nermin Ali Dr. Enas Lotfy Lec No. 1 Course Code: FAC-104 1 Page 1  CHAPTER 3 SOUND AND ULTRASOUND THERAPY 2 Page 2 Hello Can you tell me what do you see here? 3 First ❑ What is sound? ❑ What is a wave? ❑ What are the types of waves? ❑ How does sound transfer? 4 ❖ We need to understand the meaning of a wave first A wave: is a flow or transfer of energy. How does energy transfer? Types of Waves ▪ Mechanical waves ▪ Electromagnetic waves 5  Electromagnetic waves Electromagnetic waves do not require a medium to travel through but can travel through transparent media. They can also travel through “empty” space. Electromagnetic waves are Transverse Waves. Electromagnetic waves include (in increasing order of frequency), microwaves, infrared waves, visible red light, visible blue light, ultraviolet, X-rays, and gamma rays. 6  Mechanical waves Mechanical wave: is a mechanism for transferring energy through a medium (the air or water) without transferring matter. Examples: (sound waves, waves on water). Based on the orientation of particle motion and direction of energy, there are two types of waves: Longitudinal Transverse waves waves 7  ❖ Longitudinal waves In this type of wave, the movement of the particle is parallel to the motion of the energy i.e. the displacement of the medium is in the same direction in which the wave is moving. Example: Sound Waves Pressure Waves 8 9  ❖ Transverse waves When the movement of the particles is perpendicular to the motion of the energy, then this type of wave is known as a Transverse wave Examples: Light and Electromagnetic waves. 10  The components (electric and magnetic fields) of a light wave oscillate perpendicular to the direction of wave propagation. Hence, it is a transverse wave. 11  ❖ Measurable properties of waves: 1)Wavelength (symbol λ) is the distance between two successive crests (in meters, m). 2)Frequency (f) (in hertz, Hz). Or the number of waves that pass a certain point in one second. 12 3) Period or periodic time (T) (in seconds, s). The amount of time it takes for a wave to complete one cycle. 4) Speed (v) is how fast a wave is moving in the direction of propagation (in meters per second, m/s). ❑ The speed of light traveling through air is 3×𝟏𝟎𝟖 m/s, while for sound, the speed in air is about 330 m/s. In tissue, sound moves faster, at about 1560 m/s. 13 5) Amplitude (A),(in meters, m)., is the maximum displacement from the mean (or rest) position. For example, the vertical distance between a trough and a crest of a wave in water is two times the amplitude. Amplitude (or intensity) is related to the loudness of sound and brightness of the light and to the amount of energy being carried by the wave. 14 6) Phase refers to how far out of step the oscillation of one part of a wave is when compared with another part. A phase of 0° or 360° means that the two parts are in step, while a phase difference of 180° means that the two points are completely out of step. Differences in phase between the sounds entering each ear allow us to localize the source of a sound. 15  Sound waves Sound wave: is a disturbance (Energy) transfer through a medium. 1) Sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid, or solid. 2) In human physiology and psychology, the sound is the reception of such waves and their perception by the brain. 16 3) Only acoustic waves that have frequencies lying between about 20 Hz and 20 kHz, the audio frequency range, elicit an auditory percept in humans. 4) Sound waves above 20 kHz are known as ultrasound and are not audible to humans. 5) Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges. 17  Nature of Sound: The sound produced by a guitar is different from the sound produced by a drum. This is because the sound produced by different sources has different characteristics. Sound can be characterized by its frequency, wavelength, and amplitude. Frequency of sound: The number of rarefactions or compressions that occur per unit of time is known as the frequency of a sound wave. 18 ▪ The formula of the frequency of a wave is given as: Wavelength of sound: The distance between the successive compression and rarefaction is known as the wavelength of a sound wave. ▪ The wavelength of the sound formula is given as follows: Where, f is the frequency of the sound wave. v is the velocity of the sound wave. 19  Amplitude of sound ▪ The amplitude of the sound is the magnitude of the maximum disturbance in a sound wave. ▪ The amplitude is also a measure of energy. Higher the amplitude higher the energy in a sound wave. 20 ❑ Speed of Sound 1) The speed at which sound waves propagate through a medium is known as the speed of sound. 2) The speed of sound is different in different media. 3) The speed of sound is highest in solids because the atoms in a solid are highly compressed. The interaction between atoms in a particle is highly dependent on the distance between them. The higher the interaction between the atoms, the quicker the energy is transferred. As the interaction of the particles in solids is high, the speed of sound is faster than liquids and gases. 21 4)The formula used to calculate the speed of sound is given: v = d/t Where, d is the distance traveled by sound t is the time taken to cover the distance. 22  Definition of Ultrasound ▪ Sound travels as a mechanical longitudinal wave in which back-and- forth particle motion is parallel to the direction of wave travel. ▪ Ultrasound is a high frequency sound and refers to mechanical vibrations above 20 kHz. ▪ Elephants can generate and detect sound with frequencies less than 20 Hz for long-distance communication. ▪ Bats and dolphins produce sounds in the range of 20 to 100 kHz for precise navigation. 23 ▪ Ultrasound frequencies commonly used for medical diagnosis are between 2 and 15 MHz. ▪ Sounds with frequencies above 100 kHz do not occur naturally; only human-developed devices can both generate and detect these frequencies, or ultrasounds. 24  ❖ Measurable properties of waves: 1. Wavelength (symbol λ) is the distance between two Lets revise successive crests (in meters, m). Types of Waves 2. Frequency (f) (in hertz, Hz), the number of waves that pass a certain point in one second. ▪ Mechanical waves ,examples ▪ Electromagnetic waves, examples 3. Period or periodic time (T) (in seconds, s), the amount of time it takes for a wave to complete one cycle. Longitudinal 4. Speed (v) is how fast a wave is moving in the direction waves of propagation (in meters per second, m/s). Examples 5. Amplitude (A) is the maximum displacement from the Transverse mean (or rest) position. waves 6. Phase refers to how far out of step the oscillation of one part of a wave is when compared with another part. Phase is the position of a point in time on a cycle of a waveform. 25  Thank You 26 Course Code: FAC-104