Helmholtz resonance Puns

Within the resonator, the self-resonance from the airflow will be vastly stronger than the contribution from the external source, so it seems plausible that no-phase relationship will be established. However, there are still some non-linear effects in air that may cause a phase relationship to be established. Any help?

Long range shooters worry about things like the Coriolis effect, temperature, and wind direction and speed. I recently read somewhere that they must also pay attention to the resonance or frequency of their rifles barrel. Are barrels Helmholtz Resonators? If so, how does that resonance affect the bullet as it leaves the barrel?

So after learning a bunch of Helmholtz resonance from here and here

My experiment involves changing the neck length of the bottle to see how it affects the frequency when you blow over the top. Using bottles of canadian club and gin wasn't giving me any control over other variables, so I constructed my own out of an empty peanut butter jar garden tubing and silicon to seal it.

I've been trying to figure out what units to use for each element of Helmholtz equation which you can find it both of the previous links.

My jar has a

• 0.5L cavity, so 0.0063m^2

• 1.4cm diameter inside neck, so 0.014m, making the cross sectional area 0.014^2xpi

• 4cm actual neck length, so 0.04m, and using the hydraulic diameter of an annulus (0.0019-0.0014=0.005m), we get an "Leq" of 0.043

• I'm just using 343 m/s as the speed of sound in the gas

When I plug this all into the equation I get a frequency of 82.3 Hz, but the frequency that I measure is 146.6 Hz??? http://i.imgur.com/aS3mzop.png

It's definitely not about me assuming 323m/s for the speed of sound because it would have to be around 600m/s to correct it.

What is going on?

Hi there. I want to add a Helmholtz resonator chamber to my cars exhaust, to cancel some unwanted frequencies. Was hoping you guys could look over my calculations and let me know if Im on the right track with them.

Ive measured the problem frequency range to be between 90-100hz, peaking roughly at 96. Im using metric units for all calculations here.

The formula Im using is...

f = Vs / (2π) √(An / (Vc Ln))

...where f is the target frequency, Vs is the speed of sound, An is the area of the neck section, Vc is the volume of the chamber, and Ln is the length of the neck section.

To solve for the volume of the chamber, Ive rearranged to the best of my ability...

Vc = An / (Ln (f (2π / Vs)) ^2)

...and assuming speed of sound of around 570m/s (due to exhaust temperature of around 530C), a neck radius of 0.02m (2cm) and neck length of 0.2m (20cm), I can solve:

Vs = 570
An = 0.000314m^2
Ln = 0.2m
f = 96hz

Vc = 0.00281m^3

And from that volume, I can deduce some reasonable dimensions for the chamber:

rc = 0.08m or 8cm
hc = 0.14m or 14cm

Please take a look over my work, and point out anywhere Ive gone wrong with this. Of course, actually welding it together and testing will be the real confirmation. Thanks in advance, appreciate it!

I'm interesting in learning more about Helmholtz resonance. I know that blowing air across the top of an empty bottle is an example of a Helmholtz resonator, or that the body of a violin acts like a resonator. But then, apparently resonators can also be used to dampen sound. Could someone explain how the process works?

I'm using a Helmholtz resonator as a bandpass filter by placing an electret microphone at the base, opposite the mouth and sealing it air-tight with putty. It works very well for my application. I have some more in-depth questions but I keep striking out finding answers.

I want to deduce some information about angle of incidence of a point source of sound. My initial plan was to configure multiple adjacent resonators tuned to the frequency of the point source. This will work, but may be too complicated. If instead, I applied multiple mics to the inside of a single resonator, I may be able deduce at least some information about angle of incidence. I'm not sure if this is even possible. If it is, I'd need knowledge about wave propagation behavior within the resonator. What could I read to figure this out? Also, what software could use to simulate and deduce for myself?

Hey folks,

I‘m building a Helmholtz resonator to manage my room acoustics and I have some thougts about insulation material at the inside.

Does anyone has any experience with that, and likes to share it with me?

If so: Is it necessary or rather how strong is the effect? And how does it change the inner volume of the resonator?

Looking forward to your responses!

Hi,

I have a question about covering resonators with fabric. Unfortunately the front panel of our unit doesn’t look very nice and making it look nice would take a lot of effort. I was wondering if it’s okay to cover the front panel with a thin, acoustically transparent fabric, or would it affect the resonator’s function in a negative way?

Thanks in advance!

Hello guys. I recently just read (with limited understanding) this paper on perfect helmholtz absorbers
https://pubmed.ncbi.nlm.nih.gov/30710935/

I was wondering a few things:

1. can this stuff be used for the 750-2500 frequency range? I was wondering if I could print these to put in a computer case to absorb fan noises, or print stuff that would absorb fan noises in a tissue culture room.
2. What exactly is acoustic impedance? Is it like electrical impedance?
3. Are there other "perfect" acoustic absorbers?
4. Are these things like bass traps you put in rooms?
5. Where can I read more about this stuff?

I’ve seen a few post on this subreddit about this topic but none have really answered the question I’m looking for. I am a college student working on a project to make a noise canceling earbud for autistic children, the plan is to use a Helmholtz resonator to achieve this with the desired result to only cancel out noises of a certain frequency range that would cause distress to the user. Similar products do exist on the market (I’ve linked them below) that use this technology to reduce sound pressure level without muffling noise for concert goers. I am having difficulty getting a full grasp of how a Helmholtz resonator is able to attenuate sound waves and reduce the amplitude of the sound. If anyone has any experience in this field or would care to help me it would greatly apricated. https://www.discovervibes.com/ shorturl.at/hjtU4

Been reading about Helmholtz resonators and how they can be used to absorb certain frequencies of sound. So I tried to make a simple experiment using a plastic soda bottle and a tube.
I blew air across the bottle opening and came up with a resonant frequency around 230hz, using a phone app to see the frequency spike as it was resonating.
I made a hole in my tube and attached the bottle in the hole. In one end of the tube I used a computer to generate a 230hz tone.
I ran the experiment with the bottle attached and the tube with the hole plugged. It appeared to me that when the bottle was attached the resonance of the soda bottle actually INCREASED the noise level detected at that frequency.
What am I screwing up here?

also would this explode my window like an opera singer and a glass?

I calculated that a platform that's 8 by 6 by 1 foot with 2 holes 5 inches in diameter would have a tuning frequency of 21 hz.

would there be enough sound pressure along the bottom back wall of a room that's about 22 by 18 feet to make a measurable difference?

and if so would it be more effective as a bass trap to reduce a peak than to artificially boost a range?

I'm trying to figure out if it'd be worthwhile to do and if it would be more effective to design it as a bass trap rather than a bass booster. it seems like it would work to some extent at higher volumes for sure but my instincts tell me I'm not being realistic in my hoping that it could become a parasitic passive sub and would be more effective to dampen a peak than to ever boost anything.

but I don't really know why. am I wrong?

is it because a peak is something to dampen whereas a null is nothing to amplify?

I have been thinking about blowing on a bottle. I understand that the bottle acts as a Helmholtz Resonator and when excited (blown on), the tuned frequency will be audible. Can anybody explain the physics behind the angle of the excitation? It seems that maximum output is caused by a grazing flow (90 Degrees) but as the angle is moved closer to 0, the tonal output is lowered and eventually isn't produced. I can't find any literature explaining this. Perhaps a larger pressure differential is produced with grazing flow, but are there equations to express this?

Hi all,

So I made a bunch of bass traps and broadband absorbers for my square room (fuck me). This did not solve the case, so I began looking more into axial room modes. Since my room is 6" away from being a perfect square, two of the room modes are very close together at 48hz and 51hz.

So now I was put onto the idea of crafting a Helmholtz resonator to put behind my "sweet spot" where I mix from, because there always seems to be more bass back there, and almost none where I currently sit. I'm hoping this will fix the low-end frequency response of my room.

Problem is, there are no solid guides on how to make one, and no two HH resonators I've seen thus far look the same. They're like a unicorn. I never even hear or see them in sound treated rooms, why don't people use them more often?

Anyways.. does anybody know or have a trusty DIY guide on how to make one? I'm having serious trouble finding one worth a damn. I was under the impression it is just a box with a tube coming out. (pic: http://imgur.com/a/v6sgE) but seeing everything else on the internet about them has got me very confused!

Thank you in advance if you reply :D

So I've been on-and-off researching Helmholtz resonators to try and fine-tune a ukulele I'm building. Guitar bodies are similar to helmholtz resonators. Here's some studies on guitar bodies I found http://newt.phys.unsw.edu.au/music/guitar/

Does anyone have any more information on the acoustic properties of guitars?

Hey everybody,

I own a '99 NB miata and read a lot about deleting the intake resonator underneath the intake crosspipe. Many say it improves intake noise but also many say you lose 4 ft. Pounds of torque between 3k and 4k rpm. Has any of you guys done this Mod before and could report the results? I habe already removed the intake snorkel before the airbox which gave the car a nice increase in throatyness when unser full throttle.

Greetings from Germany :)

In this episode, Tom welds on a stub Helmholtz resonator just before the muffler on his Galant VR-4.

Starts at 3:03

I'm interesting in learning more about Helmholtz resonance. I know that blowing air across the top of an empty bottle is an example of a Helmholtz resonator, or that the body of a violin acts like a resonator. But then, apparently resonators can also be used to dampen sound. Could someone explain how the process works?