# Infrasound production

#### Farble

##### Member
good evening gentlemen I hope not to have the wrong section. I want to talk to you about a problem that has been bothering me for some time and concerns the production of infrasounds. So I know they are difficult to reproduce but I need them to have a more real effect in the movies. I did a lot of research and the secret lies in moving as much air as possible I could then use subwoofers inside a labyrinth reflex to increase the displaced air. Or a super pipe like those of the organ, or a bass shaker that reaches 5 hz, or even a rotary woofer but this is very difficult to create. I have listed all these methods for you precisely because I am confused. please tell me how to reproduce them. We are at Christmas, give me a nice gift

#### buggers

##### Member
That is a very broad and non specific question. Are you asking How to reproduce a 5Hz signal? There are many ways to make that happen. Where are you trying to do this? How much money are you going to spend? What are the exact dimensions of a box that you can work with? A lot more information from you is needed...

#### GM

##### Member
Since the room normally dominates down low, one first has to measure, or at least calculate, an approximate room gain curve to even begin designing a suitable infra bass system; otherwise, as you noted, there's 'no replacement for displacement' and from very dim memory it takes a ~64 ft^3 vented cab and ~128 ft^3 sealed cab just to get to 10 Hz, so ~4x these for 5 Hz IIRC (can't find the math ATM), i.e. think large walk-in closet size at minimum IME.

That, or lots of high Xmax sub-woofers and the kilo/mega watts required to drive/cool them.

Regardless, in a massive/rigid, well constructed room with airlock doors, etc., the room gain curve begins below its lowest eigenmode/longest parallel dimension, so for instance it's 25 ft = ~1130/2/25 = ~22.6 Hz and below this point the room gain will in theory rise at 12 dB/octave (2nd order in XO parlance) = ~11.3 Hz, ~5.65 Hz, etc., so need ~2.322 octaves of ideal room gain:

Fl = Fh/2^n

n = ln(Fh/Fl)/ln(2)

where:

Fl = lower frequency
ln(2) = 0.6931

But! We're talking bomb shelter or similar room construction, so as a general rule best to design based on ~6 dB/octave (1st order) for a concrete slab home and only ~3 dB/octave for a 'floating' floor foundation home like mine (best I've measured is ~4 dB/octave and then only to ~14 Hz, the lowest system I've built).

Driver wise, unless compression horn loaded, not a good plan overall to use a point source driver below ~ a 0.5 octave (~0.707x) below its Fs, so considering just using readily available subwoofer drivers, for now either low tuned sealed or some form of compression horn with the number of drivers yet to be determined.

From this we see that one normally wants a small room with no windows, single entry door to go this low at a reasonable sub system size/cost, so till much more info is available, the question is limited to 'how low can you afford to go?'

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#### Farble

##### Member
Since the room normally dominates down low, one first has to measure, or at least calculate, an approximate room gain curve to even begin designing a suitable infra bass system; otherwise, as you noted, there's 'no replacement for displacement' and from very dim memory it takes a ~64 ft^3 vented cab and ~128 ft^3 sealed cab just to get to 10 Hz, so ~4x these for 5 Hz IIRC (can't find the math ATM), i.e. think large walk-in closet size at minimum IME.

That, or lots of high Xmax sub-woofers and the kilo/mega watts required to drive/cool them.

Regardless, in a massive/rigid, well constructed room with airlock doors, etc., the room gain curve begins below its lowest eigenmode/longest parallel dimension, so for instance it's 25 ft = ~1130/2/25 = ~22.6 Hz and below this point the room gain will in theory rise at 12 dB/octave (2nd order in XO parlance) = ~11.3 Hz, ~5.65 Hz, etc., so need ~2.322 octaves of ideal room gain:

Fl = Fh/2^n

n = ln(Fh/Fl)/ln(2)

where:

Fl = lower frequency
ln(2) = 0.6931

But! We're talking bomb shelter or similar room construction, so as a general rule best to design based on ~6 dB/octave (1st order) for a concrete slab home and only ~3 dB/octave for a 'floating' floor foundation home like mine (best I've measured is ~4 dB/octave and then only to ~14 Hz, the lowest system I've built).

Driver wise, unless compression horn loaded, not a good plan overall to use a point source driver below ~ a 0.5 octave (~0.707x) below its Fs, so considering just using readily available subwoofer drivers, for now either low tuned sealed or some form of compression horn with the number of drivers yet to be determined.

From this we see that one normally wants a small room with no windows, single entry door to go this low at a reasonable sub system size/cost, so till much more info is available, the question is limited to 'how low can you afford to go?'
thank you gentlemen of the answers. Then I too had already thought about the wardrobe but the dimensions are too big and then 5 hz is not the absolute value but the only thing that interests me is to abdicate below 20 hz. Another way that I can use to make it portable enough is to use pipe cones for example those of organ (Musical instrument) in which a 9 meter pipe can reproduce 16 hz also because, the pipe can also be wound. I am interested in hearing the effect a few meters away and I have a budget of up to \$ 200, so I would like a home solution. So the fact of the Rotary woofer is a prohibitive idea. The bass shaker could be the most plausible choice but I don't know its limits and that is, can I hear infrasound at 2 meters away? So as you understand, I'm interested in something mechanical just to not spend a lot. I have heard that there are nebulizers that create infrasound and smoke, but I don't know about this

#### Farble

##### Member
That is a very broad and non specific question. Are you asking How to reproduce a 5Hz signal? There are many ways to make that happen. Where are you trying to do this? How much money are you going to spend? What are the exact dimensions of a box that you can work with? A lot more information from you is needed...
the solution I am looking for is "mechanical" in the sense that I would like to use bass shakers, pipes or anything else that I do not know, in fact I am asking you in order to spend little. Rotary Woofers would be the best solution but they are difficult so I choose other solutions. I would like it to be a minimum portable, and 5 hz is not a constant but the important thing is that it is infrasound below 20 hz. The dr. Gavreau in his experiments du succubus of a faulty engine and later created an instrument to produce infrasound, perhaps he had the solution.

#### johnmath

##### Member
Infrasound is felt rather than heard. Moving enough air to get the level of feeling needed is an extremely inefficient means to a result. Better to use shakers.

In order for the audience to feel vibrations, there has to be some resilience in the surface the audience is on. This can be achieved by making a platform floor on vibration mounts. This is how its done professionally for simulators such as earthquakes or rockets. I've been on the Awaji Island (Japan) earthquake simulator pictured new the bottom in this link https://www.japanvisitor.com/japan-museums/hokudan-earthquake-memorial-park and the effect is quite terrifying.

In 1999/2000 I working on a project in for a space themed restaurant that had a simulated rocket takeoff between the ticket counter (reception) and the restaurant (spaceship), which also used a platform floor driven by shakers. Inside the restaurant people sat in booths with a touchscreen entertainment system that could play music clips, etc. I designed, prototyped, constructed and installed the booth sound systems. In order to keep "crosstalk" between booths to a minimum, acoustic priciples and directional loudspeakers were used and bass was reproduced by shakers in the seats, rather than acoustically, although there was no specific attempt to go subsonic in the bass response. By collaborating with the interior designers and the mechanical construction of the benches the result was very impressive, even if I do say so myself.

Edit: I should have said the shakers cost only about \$20 each at the time and IIRC six were used in each booth, each driven with a chip amp; the secret is in the resilience of the seats.

https://www.tectvs.com/xerts

#### johnmath

##### Member
I'd forgotten in my post above there was a seventh shaker in the table top in each booth. This was crossed at 200Hz from the controlled directivity louspeaker located under the screen, thereby causing the tabletop to provide near-field bass reproduction for the booth occupants to fill in the frequencies above those generated by the shakers in the seats. In one the photo you can see the concentric rings of acoustic absorption we used to control ceiling bounce between booths.

#### freddi

##### Member
Paid Member
fwiw here's one method, if not a solution. I looked at the least inexpensive 21" Dayton woofer. A huge series BP6 appeared worthless.

I do like a simple low tuned 600l bass reflex with lowpass applied near Fb

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#### Farble

##### Member
Infrasound is felt rather than heard. Moving enough air to get the level of feeling needed is an extremely inefficient means to a result. Better to use shakers.

In order for the audience to feel vibrations, there has to be some resilience in the surface the audience is on. This can be achieved by making a platform floor on vibration mounts. This is how its done professionally for simulators such as earthquakes or rockets. I've been on the Awaji Island (Japan) earthquake simulator pictured new the bottom in this link https://www.japanvisitor.com/japan-museums/hokudan-earthquake-memorial-park and the effect is quite terrifying.

In 1999/2000 I working on a project in for a space themed restaurant that had a simulated rocket takeoff between the ticket counter (reception) and the restaurant (spaceship), which also used a platform floor driven by shakers. Inside the restaurant people sat in booths with a touchscreen entertainment system that could play music clips, etc. I designed, prototyped, constructed and installed the booth sound systems. In order to keep "crosstalk" between booths to a minimum, acoustic priciples and directional loudspeakers were used and bass was reproduced by shakers in the seats, rather than acoustically, although there was no specific attempt to go subsonic in the bass response. By collaborating with the interior designers and the mechanical construction of the benches the result was very impressive, even if I do say so myself.

Edit: I should have said the shakers cost only about \$20 each at the time and IIRC six were used in each booth, each driven with a chip amp; the secret is in the resilience of the seats.

https://www.tectvs.com/xerts
thank you gentlemen first of all I want to thank you for the help you are giving me after so many forums that have not helped me. I am not an expert in this area and in fact I do not know which is the best solution, but at the level of mathematical calculations they are not difficult. So I say my opinion the bass shakers are portable but I don't know if they can work in open environments, being close to the bass shaker. These in fact exploit the technology of Tesla vibrating tables and it is said that it works very well or as diesel engines and a bus passes near my house and I must say that you can hear the infrasound quondi the bass shaker can be a valid choice but there are some problems like for example does it work well outdoors? how much power does it have?

#### Farble

##### Member
fwiw here's one method, if not a solution. I looked at the least inexpensive 21" Dayton woofer. A huge series BP6 appeared worthless.

I do like a simple low tuned 600l bass reflex with lowpass applied near Fb
good evening fred, I will answer you each at a time because I believe that every solution is excellent you just need to choose the best. So as for your proposal 600 liters are really many and I can hardly transport it, so to remedy we can use a transmission line to contain better or a double bass reflex that seeing technical drawings on the internet, I think it has smaller dimensions and a revolutionary design. Obviously you tell me how to wait for your answers

#### johnmath

##### Member
A shaker is simply a transducer coupled to a moving mass. To impart a vibration that can be felt the shaker needs to be coupled to a surface that will create a counter/reactionary motion, and that surface needs to be coupled in turn to the 'listener', for example by them sitting or standing on the vibrating surface. Dayton Audio make a range of tactile drivers for attaching to surfaces. See: https://www.daytonaudio.com/search?searchterm=tactile

I have seen wearable transducers inside a jacket for gamers, called haptic suits. These are designed to be worn during virtual reality games so the player can feel explosions and bullets, etc. See: https://en.wikipedia.org/wiki/Haptic_suit

#### bobdebouwer

##### Member
did you already check out the (hover)boss topic on avsforum? There is a lot of information on infrasonic sound reproduction there.

Realistically though, 200 usd budget? That does not even pay for an amplifier.

#### Farble

##### Member
Uno scosso è semplicemente un trasduttore accoppiato a una massa in movimento. Per dare una vibrazione che si può sentire lo scuoter deve essere accoppiato a una superficie che crei un movimento contro/reattivo, e che la superficie deve essere accoppiata a sua volta all'ascolto, ad esempio da loro seduti o in piedi sulla superficie vibrante. Dayton Audio fa una serie di autisti tattili per l'attacco alle superfici. Vedi: https://www. daytonaudio. com/search? searchterm=tattile

Ho visto trasduttori indossabili dentro una giacca per i giocatori, chiamati abiti haptici. Questi sono progettati per essere indossati durante i giochi di realtà virtuale in modo che il giocatore possa sentire esplosioni e proiettili, ecc. Vedere: https://en. wikipedia. org/wiki/Haptic_suit
good evening john i'll answer you now because i had problems with the provider. So the bass shaker for example I can not place it directly on the floor of the house and hear the infrasound at a distance of one meter? just this configuration is enough or do you have to add the Tesla style vibrating table? Also why would the idea of the bass shaker seem the best idea, and then the infrasounds even if they travel on the ruesco ground to hear them well?

#### Farble

##### Member
Hai già controllato il tema (hover) Ci sono molte informazioni sulla riproduzione del suono infrasonico.

Realisticamente, però, 200 usd budget? Questo non paga nemmeno per un amplificatore.

Qual è la tua attuale configurazione, cosa hai già?

Buonsera Bob non so a cosa si riferisce con il ma hover, ma sarei curioso, mandami il link. Per quanto riguarda la mia attuale attrezzatura ho un semplice subwoofer d'auto, che raggiunge i 100 hz, che è del tutto irrealistico per l'infrasuzione.

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#### johnmath

##### Member
good evening john i'll answer you now because i had problems with the provider. So the bass shaker for example I can not place it directly on the floor of the house and hear the infrasound at a distance of one meter? just this configuration is enough or do you have to add the Tesla style vibrating table? Also why would the idea of the bass shaker seem the best idea, and then the infrasounds even if they travel on the ruesco ground to hear them well?
The reason is efficiency. By definition infrasonic sound is felt, not heard with your ears. You'll need a ton more power to get the same effect with air-coupled infrasonic sound than a physical connection to the infrasonic transducer, I suspect something like 10 to 100 times more amplifier power.

The difference between air coupling and a physical coupling to the transducer is comparable to holding your hand in front of the bass driver cone and actually touching the bass driver cone with your fingers - a huge difference in the level of sensation.

Infraflex!!!

#### Farble

##### Member
The reason is efficiency. By definition infrasonic sound is felt, not heard with your ears. You'll need a ton more power to get the same effect with air-coupled infrasonic sound than a physical connection to the infrasonic transducer, I suspect something like 10 to 100 times more amplifier power.

The difference between air coupling and a physical coupling to the transducer is comparable to holding your hand in front of the bass driver cone and actually touching the bass driver cone with your fingers - a huge difference in the level of sensation.
first of all I wish you a happy new year. In these days of celebration I have also thought a lot and I must say that portability is important. I therefore decided to have more solutions, and therefore I chose the bass shaker and the transmission line. So John you convinced me to choose the bass shaker, which one should I buy and which configuration to use ??

#### tvrgeek

##### Member
Providing you have any source with those frequencies. But when I had a "mere" pair of 12 inch XLXX, I could feel below what I could here. Driven my "only" a Parasound 2200. Talking probably 20 to 30. More pressure in your chest. 10 Hz will cause your bowls to let go.

#### peril

##### Member
infraflex you can find with Google. Etienne the inventor. Membrane with 1 qm