Thank you for the examples with simple demonstrations

Always wondered how it is measured. Got clear answer with a way to measure it myself. I will share this video to my knowns who are studying in 11-12. Such a great way to explain.

Excellent explanation!

Srinath don't mean to be rude or anything, but you are the best English speaking Indian I have ever heard his accent. I watched your video with joy, I salute you!

Most underrated explanation thank you so much

Well explained !!

Very helpful, thank you.

Really amazing video

nice

How precise is that method? Because there are equations to find natural frequency too

@SrinathSrinivasan

4 жыл бұрын

Hello, Thank you for watching the video. The method that was demonstrated was to capture the sound waves emitted by the beaker after exciting it and thereby determine its natural frequency. This however is only a crude way to quickly determine the approximate natural frequency.

Explanation was very impressive. Which app used on mobile during explanation

@SrinathSrinivasan

3 жыл бұрын

Hello, It is "VisualAudio" version1.0.3 in ios.

@yeswanthbabud2622

3 жыл бұрын

@@SrinathSrinivasan sir, can you recommend such app for android too?

@SrinathSrinivasan

3 жыл бұрын

For android, I'd suggest "Spectroid" app.

what's the difference between the swing and pendulum? I think they are very similar

@SrinathSrinivasan

2 жыл бұрын

Yes they are. A swing oscillating by itself after an initial excitation is also exhibiting free vibration.

I've been through a lot of videos but I still didn't get one thing... Free oscillation is when a body which is initially disturbed vibrates but doesn't it's frequency depend upon the force applied initially? Like greater the initial disturbance greater the frequency? How's the natural frequency same all the time? Can you please help me with this doubt?

@SrinathSrinivasan

3 жыл бұрын

Hello, Thank you for watching the video. As far as the math goes, Natural frequency of an object or a system is a function of mass and stiffness but independent of the initial excitation. An object or a system when excited oscillates only at one particular frequency which is the natural frequency regardless of the magnitude of excitation. Consider an example of human vocal folds. Vocal folds is the voice box which is excited by air from the lungs. Male vocal folds are longer while female vocal folds are shorter. This is the reason why male voice is low-pitched while female voice is high-pitched regardless of how loud their output voice is. If frequency were to depend on intial excitation, both male and female voice pitch would keep changing as a function of initial excitation. It doesn't happen like that, does it?

@Dr.freedom

3 жыл бұрын

The same doubt I also have. Srinivasan Sirs explanation is partially okay. For eg: if a steel beaker with a certain mass M and stiffness K is kept on a table, math-wise the natural frequency F would be "SquareRoot of K/M". However, if we are not disturbing it, and if we would keep a accelerometer (or an app) on it, it would record nothing. It would record the frequency only if we disturb the steel beaker with a external force. Why is this so? How to measure Squireroot of K/M physically?

@hmata3

2 жыл бұрын

@@Dr.freedom Natural frequency is an inherent property like K in a spring. You won't know the K constant is a spring without exerting a force in it. Similarly, you can't measure natural response without applying energy to make it vibrate. You will need an accelerometer to measure its natural frequency like you need a ruler to measure the elongation of a spring.

Can u please explain the difference between natural and applied frequency and what does it mean if they have the same value?

@SrinathSrinivasan

2 жыл бұрын

Natural frequency is the frequency at which a body or a system tends to vibrate freely after it is given an initial excitation. An initial excitation is required as the body/system cannot start vibrating by itself. Here we can say that the body is exhibiting 'Free vibration'. 'Forced vibration' on the other hand is when there is an external driving force on the body, forcing it to vibrate under its influence. The input frequency here is the Forced frequency or applied frequency. When both are equal, it leads to a phenomenon called "Resonance" wherein the body vibrates violently with maximum amplitude before rupturing. A good example would be an Opera singer breaking a wine glass with her voice.

@asheshgupta4845

Жыл бұрын

​@@SrinathSrinivasan sir so regardless of initial excitation, the frequency would be same?

@SrinathSrinivasan

Жыл бұрын

Yes.

Can you please explain to me how frequency depends only on the source of sound and not energy? Great video by the way!

@SrinathSrinivasan

4 жыл бұрын

Hello, Thank you for watching the video. Natural frequency of an object depends only on an object's stiffness and mass. It is a characteristic of an object and does not depend on the excitation force. If any of the above two variables are changed, then the natural frequency will change. For example, in the video, if the beaker was filled with water, the natural frequency will be different despite using the same spoon to impact since the mass has now increased.

@gowrimuguli5972

4 жыл бұрын

Thanks a lot!

@jacobvippond5532

4 жыл бұрын

Srinath Srinivasan out of curiosity, how would you measure the stiffness of an object?

@SrinathSrinivasan

4 жыл бұрын

Hello, Stiffness is force per unit length. In the equation F = kx, F is the force, x is the elongation or compression and k is the stiffness. Higher the stiffness, more is the force required to achieve the desired elongation. Stiffness cannot be measured directly like length rather it is determined by experimentation. Consider a spring subjected to a given load. Measure the elongation and plug in the values in the above equation to determine stiffness. For complex systems with different material densities, a computer simulation would be ideal.

@hmata3

2 жыл бұрын

@@SrinathSrinivasan Great video! Wanted to ask: after some empirical evaluations, I've seen that stiffness may not have a significant influence natural frequency. Though it was not a large study, do you think natural frequency can be influenced by several different factors, like density, shape, or temperature? Again, thanks for the great informational video and your feedback!

Love your accent!

How can we be sure that it is the natural frequency of the beaker and not of the spoon?

@SrinathSrinivasan

4 жыл бұрын

Hello, Thank you for watching the video. The Natural frequency of an object or a system is relevant only when the object in question is undergoing a free oscillation. When an object is given an initial excitation, the object oscillates freely (like the simple pendulum). An oscillation with a constant external force or damper is not a free oscillation. In the above video, when the beaker was impacted with the spoon, both were excited. Since I was holding the spoon, my hand was damping the spoon's vibrations and not allowing the spoon to vibrate freely. On the other hand, I was holding the beaker (with least contact) at the base while the lip of beaker was free. Basically the beaker was free to vibrate with no external dampers to dampen its vibration. These vibrations produce sound waves which are captured by the Spectrum analyzer. This however is an approximate way to determine the natural frequency. The best way would be to use a calibrated impact hammer.

@m_tahseen

4 жыл бұрын

@@SrinathSrinivasan Well explained. You hv provided no info in the 'about' section . What do u do, if I may ask ?

@SrinathSrinivasan

4 жыл бұрын

I'll be updating my bio soon. You can check it out.

What about direction/placement of impact? How does that relate to the natural frequency?

@SrinathSrinivasan

4 жыл бұрын

Hello, Thank you for watching the video. As explained in the video, there are 3 methods to determine the natural frequency. The demonstration with beaker and spoon is method 2 where we are relying completely on the sound waves to make an estimate of the natural frequency of beaker. In this scenario, the direction of impact is not important because sound is a scalar and it is omnidirectional (radiates in all directions). No matter where you hit, sound waves are created and are detected by the spectrum analyzer. However if method 1 is to be used which is using an impact hammer and a triaxial (x,y,z axis) accelerometer, the directions become important as we are dealing with vectors. Both the direction of hit and direction of accelerometer have to considered with care. This would reflect in the response plot and thus the natural frequency determination.

@KH-ft4ut

4 жыл бұрын

@@SrinathSrinivasan Thank you very much for taking the time to reply. Just to clarify, your saying that with method 1, you risk getting a false readings due to incorrect sensor placements. But if you could get perfect readings, the direction of impact would not matter for any object. The only thing that would change is the amplitude and possibly dampening effect?

@SrinathSrinivasan

4 жыл бұрын

An impact hammer measures force while accelerometer measures acceleration. Both measurements are vectors. The hammer is the input whereas the accelerometer is the output. Directions are important for both. You are exciting a structure using a hammer and measuring its response using the accelerometer. Complex structures have multiple natural frequencies also referred to as 'modes'. These modes may be present in any plane (x-y;y-z or x-z). So for this reason, direction of hit also matters in order to determine in which plane is the structure vibrating. Also how hard you hit won't change your readings.

@KH-ft4ut

4 жыл бұрын

@@SrinathSrinivasan Thank you very much for clarifying :)

@SanthoshKumar-wx9xx

3 жыл бұрын

Sir, please tell me about modes

in the second method you would have to factor in that your using stainless steel on the beaker to produce the sound

@SrinathSrinivasan

2 жыл бұрын

No. The purpose of using stainless steel spoon was to give the beaker an initial excitation so that the beaker vibrates and produces sound. The beaker will still generate the same frequencies when excited with say a plastic pen instead of a stainless steel spoon. This is because Natural frequency of the beaker is a property of the beaker's mass and stiffness and not the material which was used to give it an initial excitation.

when you say "initial excitation" and then you say "without the aid of the external force"..... Initial exciation is not an external force? anyone please help

@SrinathSrinivasan

2 жыл бұрын

Let me explain with an example. Consider a child sitting on a swing and a person ready to push the swing. Case1: The person just pushes the swing once. In this case, he is giving the swing an initial excitation. An initial excitation is required as the swing will not move by itself. After giving initial excitation, the swing oscillates back and forth at a certain frequency. This frequency is the natural frequency of the swing system. Case2: The person pushes the swing every single time. In this case, he is applying force every time is pushing the swing. The result is a forced oscillation since the swing is no longer oscillating by itself but rather under the influence of an external force.

Are u a scientist?

Who knew?