Class 11 Physics (India)
- Production of sound
- Sound Properties: Amplitude, period, frequency, wavelength
- Speed of Sound
- Relative speed of sound in solids, liquids, and gases
- Decibel Scale
- Why do sounds get softer?
- Ultrasound medical imaging
- Standing waves in open tubes
- Standing waves in closed tubes
- Wavelength and frequency for sound waves in tubes
- Pressure and displacement of sound waves in tubes
- Introduction to sound review
Ultrasound medical imaging
Ultrasound medical imaging (also known as sonography) is a diagnostic imaging tool that uses high-frequency sound waves to create images of structures in the body. Ultrasound images are captured in real time using an external probe and ultrasound gel placed directly on the skin. They can show things that a still image like an X-ray cannot, such as blood flow or organ movement. Ultrasound images are highly useful in the diagnosis and treatment of many diseases. Created by David SantoPietro.
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- okay!! we can't hear ultrasounds.. but why don't ultrasounds damage our ear drum??(34 votes)
- I guess because everything has a resonant frequency, that is a frequency that it vibrates at easily due to its construction, springiness, shape and density. I'm thinking the mechanisms in the human ear do not resonate well at ultra-sonic frequencies, so in order to do damage you would need a much higher amplitude than is needed for say a 3.5KHz signal. The ear picks up 3.5KHz really well - most of the frequency content of my mum's voice is around this frequency. I'm sure my mum's voice at 80dB could do damage to anyone's ear mechanism, but I'm also sure if you had an ultrasonic signal and played it at 150dB you would also do damage.(4 votes)
- How about infrasounds? What are they used for?(14 votes)
- Sometimes it's used for long distant communications(17 votes)
- Why do higher frequencies experience less diffraction? I'm trying to imagine, physically, why more frequent waves would spread out less.(12 votes)
- High frequency waves have Low wavelengths. This results in lesser chance of it spreading out as the wave fronts are very close to each other.(8 votes)
- Why does ultrasound reflect when it encounters a different medium? Does this happen with audible sound as well?(4 votes)
- Whenever a wave encounter a surface that separates 2 mediums, you can observe a reflection. The amplitude of the reflected wave depends on the medium's properties(which affect the wave's propagation speed). If a medium is much denser than air or flesh (like bones) , the amplitude of the reflected sound wave increases, and the detection is better for ultrasound waves. Nevertheless, the reflection happens for every wave, even electromagnetic waves.(9 votes)
- What is the practical use of ultrasonic industry application..?? And how is it done.??(4 votes)
- What Isabelle said here is just right, but there are a ton of other uses, radars for boats, used in fishing, in weaponry, in surgeries, in cleaning of long tubes that are hard to reach, used in detecting defects in machinery or buildings, etc. so you see, ultrasound plays an important role in industry applications.
For the second part of your question, ultrasound is just passed through objects or sent to reach specific objects you want to use ultrasound on. Like tubes, for example, may be kept in vacuum, and ultrasound is let on them.
Hope it answered your question!(7 votes)
- why dont the sound ways get reflected from furniture and why they get reflected from the walls(2 votes)
- Why don't sound waves refract in the body ?
TEACHER MACKENZIE said that sound refracts at different mediums , because aren't the tissues & blood different mediums(3 votes)
- yes. Great thinking!
You are right. Sound waves DO refract and reflect in the body. This is how we are able to see different organs and layers of tissue in the body using ultrasound....high frequency sound waves.
- Is there any way that you can raise the wavelength besides lowering the speed or the frequency?(1 vote)
- the only way that you can change the speed is through a different medium or by changing the medium itself. therefore you can change the wavelength by changing the medium through which it travels. since wavelengths are changed by frequency and speed(therefore medium) there shouldn't be another way that a wavelength can be changed.(6 votes)
- if light waves can go through the process of refraction can sound waves get refracted too?(2 votes)
When the sound waves pass from a dense medium to a less dense medium, the speed will change and so refraction can occur. sound travelling through different layers of the atmosphere or oceans for example.
Hope that helps
- but if ultrasound is to high for our ears to hear can other animals hear it particularly dogs and bats(2 votes)
- Bats can hear frequencies up to 200,000 Hz and dogs can hear up to 45,000 Hz. Ultrasound's frequency is at about 20,000 Hz so both dogs and bats can hear it.(4 votes)
- [Voiceover] The human ear can hear frequencies from around 20 hertz to about ... 20 hertz is a very low base ... to up to around 20,000 hertz. This is way up there. If it's a frequency above this, this is the range we can hear, if the frequency lies above this range, we give it a special name. We call it ultrasound, or ultrasonic. This does more than just annoy animals. This has a practical purpose. If you wanted to do some medical imaging or figure out what's going on in the human body ... So, say, here's a portion of the human body and there's maybe a vital organ or some tissue here, or some tissue over here, you're worried something's going wrong, you got to figure out what's going on inside, you can operate, but that obviously sucks. You want to try to avoid an operation if possible. You can do x-ray, but too much exposure to radiation is bad, too, so a very good option is usually ultrasound. We can take what's called a transducer. We put that transducer up to the skin. This transducer takes electrical energy, you plug it into the wall, turns it into sound energy. You send out sound waves. You send out a pulse. This transducer sends out a pulse. This pulse travels toward anything in here, and it turns out it'll reflect. It'll reflect any time there's a difference in the medium, so any time there's an interface between the two media, which, in this case, we'll make it simple. Let's just say there's tissue from blood or other things, or, sorry, tissue from organs, and then the red will represent the blood. This is going to keep traveling here, it keeps traveling. Once there's an interface, here, between blood and tissue, it will reflect, comes back. This transducer's always timing. It knows when it sent out the pulse and it knows when that pulse got reflected back. It also knows the speed of sound, so it can calculate, all right, if it took that long to get back, it must have reflected this far away. Something's at this point. That's done yet, though. Some of this wave is going to travel on. In fact, most of this wave travels through, keeps going. Here's another interface between tissue and blood, so it's going to reflect again. This reflects back. We'll get another pulse. This is at some later time. The transducer knows, all right, took that long, now there must have been something else there. My one pulse got reflected two times. So there's something here, and here's the end of it. But that's not done either. This keeps on going. It'll reflect against this interface between blood and tissue. I'm drawing these sound waves crooked just so you can see them. They'd really be right on top of each other along this line. That takes another amount of time. It keeps doing this and it knows that you'll have points right here, difference between interfaces right here, an interface between two different tissues. You can get an image of this whole cross section. If you just have a transducer that sends out pulses along this whole face of the transducer you can image this whole region. So you can start imaging all these points. You can figure out what is inside of here, what's the shape of it, what are any particular lesions or lumps going on inside of here. That's ultrasound. That's one way it's useful. It actually uses ultrasound frequencies. You might wonder why. Why would we have to use ultrasound? One reason why is if you took this transducer and you were using audible frequencies, you take this noisy thing, you hold it up to a patient, that patient's going to be like, "Uh, are you sure that's okay to hold up to me, doc?" That might be upsetting. Another more practical reason for using ultrasound is high frequencies, and that is to say low wavelengths, and these two are the same because, remember, speed of a wave is wavelength times frequency, so if the frequency's high, the wavelength is low, because the speed's not determined by either of those. The speed is determined by the medium itself. It turns out, for high frequency, low wavelength, you get less diffraction. Diffraction is an enemy of making clear pictures because what diffraction is, is this is a spreading out of waves. If I had my wave coming in here, wave coming in, and there was some sort of barrier, let's say this barrier is right here, and I've got a small hole in it, waves spread out. But if it's a high frequency wave, it won't spread out much. It's going to enter through this hole and it'll spread out a little bit. It's going to get a little bit wider. But, if it were a low frequency, maybe audible region high wavelength, the spreading would be bigger and this would be a problem because if it spreads out, think about it, if this wave was coming in here and this wave is coming in here, and then it curves around corners. Another thing diffraction does is it causes waves to curve around corners, the spreading happens, now you've got all this bending of sound waves, sound waves reflecting off of things confusing the transducer, you get a blurry image. That's why we want to use high frequencies. There's less diffraction, you get a clearer image. This is one application of ultrasound for medical imaging.