Axel1966
Thu 23 February 2012, 15:04
Hi all,
As i'm graduated in sound engineering and achitectural acoustics, I've been asked to post solutions to quiet a vacuuming system.
Sorry if this post is in the wrong place, feel free to dispace it.
First, what is sound ?
Noise is some sound. A sound is a vibration propagated into air, like a weave can propagated into water. You can hear or feel sound. Apreciate, all the vibrations surrounding us may not be heared. A standard people can hear frequencies in a range between 22 to 20.000 hz. Most of peoble can feel low frequecies from 16 to 40 hz. 16hz is the sound produced by the tallest pipe of a classical church organ. Audition is the only sense which is never disconnected. You can rest your vision by closing your eyes, but you can't turn off your ears. You wake up not by a smell or a touch, but by the sound of your alarm clock.
Noise is a public and personal enemy
Human brain acts as a filter. It helps to focus on important sounds (talks) but noise still exists and have a real influence on you hearing capacity. The more noise you will stand during your life, the more, the fast, you will lose your hearing ability. You can easily understand you see or read with difficulties, but you'll never understand by yourself you have hearing problems, because human brain still manage the sounds to help you analyse your acoustic environment, much better than you hear in reality. Ears never regenerate. You must preserve your hearing capital. Apreciate, humans have ears adapted to a quiet tropical forest, nothing else.
Otherhand, sound pollution is a disaster. Noise can turn anybody mad easily. If you can stand heavy noises (maybe because of a lack of hearing ability), your neighborhood may not. A noise may be standable in a close location, while it can be louder several meters or rooms away.
You'll get tired more, and more quickly, in a noisy environment. A noisy workshop can even disturb outside of the workshop, creating conflits inside and outside. It's good to kill noise wherever it is.
Sound propagation
Sound have two ways of propagation. First, direct or air propagation. Second, propagation through solids. (See fig. 1)
http://giemastruc.free.fr/Forums/SoundPropagation.png
Air propagation don't need to be explained. Propagation through solids can be considered as chain reactions. A vibration can progress inside an object, then progress into another one in contact with the first one, and so on. Each object can resitute the vibration by vibrating itself. As example, when you talk to someone through a simple window, the sound of your voice vibrates in the air, then the air hit the window, then the window vibrate and transmit your voice through the outside air, which will be recieved by your listener. He hears your indirect voice.
Sound insulation
Sound insulation is not the same than heat insulation. The second is quite simple, and may have questionable results on sound. Otherhand, a good sound insulation is always an excellent heat insulation. A total sound insulation needs heavy implementation, very expensive most of the time, pervection is close to be impossible. Let's rather talk about sound reduction, which is much more reachable.
A good sound insulation is focused on three axis :
Prevent propagation through solids
Limit air propagation
Sound absorbtion (quieting)
1/ as sound may travel through solids, the goal is to lock the vibrations inside the solid. The method is simple : isolate the solid from others objects, with an antivibratory base or an antivibratory suspension.
2/ now we may limit air propagation. Another simple method : create an antivibratory environment within sound will be trapped. Generaly soft surfaces.
3/ Absorbant surfaces, like foam or mineral whool, can absorb vibrations by division. If the surface and path is large enough, a spectacular sound reduction can be conducted.
Note it's easy to reduce medium to high frequencies. Low frequencies needs more mass and surface to be reduced. If you have to manage low frequecies, better look at a way to limitate their early propagation/generation.
This are general principles, not a sound insulation bible. ;)
Quieting a Vacuum system
At last, we're ready to give an application of the above.
First, the best way to manage noise is to avoid creating some. So, a simple electric relay will make the vacuum start simultaneously as the MM spindle. No vacuuming needed ? No vacuum noise...
http://giemastruc.free.fr/Forums/VacuumIsolation.png
Second, think "box in a box", open space, means propagation (dust, smell, noise...). The best way to manage propagation is to manage environment.
It is right for a vacuum system, right for a MM, even if it takes more place and you may think about comfortable access to the machines. Think you don't have to access the vaacum tray frequently, and the MM can cut for a long time within your close presence.
Note the care needed to isolate in/outs (tubes, cables). Through, the noise trapp's path needs to be as long as possible for a better noise reduction.
About 's'.
'S' is a surface value in mē, needed for a good air flow.
Air flow can make noise by itself. It would be pittyfull to add noise while reducing some...
'S' is calculated from air speed (must be inferior than 20km/h to avoid grid whistling) and air flow.
The calculation is :
Air flow (m3/h) / 20 (km/h) / 1000 = grid surface and noise trapp section (mē)
I wish my english was good enough to make this topic helpfull for members.
I'll try to awnser any question.
Regards.
As i'm graduated in sound engineering and achitectural acoustics, I've been asked to post solutions to quiet a vacuuming system.
Sorry if this post is in the wrong place, feel free to dispace it.
First, what is sound ?
Noise is some sound. A sound is a vibration propagated into air, like a weave can propagated into water. You can hear or feel sound. Apreciate, all the vibrations surrounding us may not be heared. A standard people can hear frequencies in a range between 22 to 20.000 hz. Most of peoble can feel low frequecies from 16 to 40 hz. 16hz is the sound produced by the tallest pipe of a classical church organ. Audition is the only sense which is never disconnected. You can rest your vision by closing your eyes, but you can't turn off your ears. You wake up not by a smell or a touch, but by the sound of your alarm clock.
Noise is a public and personal enemy
Human brain acts as a filter. It helps to focus on important sounds (talks) but noise still exists and have a real influence on you hearing capacity. The more noise you will stand during your life, the more, the fast, you will lose your hearing ability. You can easily understand you see or read with difficulties, but you'll never understand by yourself you have hearing problems, because human brain still manage the sounds to help you analyse your acoustic environment, much better than you hear in reality. Ears never regenerate. You must preserve your hearing capital. Apreciate, humans have ears adapted to a quiet tropical forest, nothing else.
Otherhand, sound pollution is a disaster. Noise can turn anybody mad easily. If you can stand heavy noises (maybe because of a lack of hearing ability), your neighborhood may not. A noise may be standable in a close location, while it can be louder several meters or rooms away.
You'll get tired more, and more quickly, in a noisy environment. A noisy workshop can even disturb outside of the workshop, creating conflits inside and outside. It's good to kill noise wherever it is.
Sound propagation
Sound have two ways of propagation. First, direct or air propagation. Second, propagation through solids. (See fig. 1)
http://giemastruc.free.fr/Forums/SoundPropagation.png
Air propagation don't need to be explained. Propagation through solids can be considered as chain reactions. A vibration can progress inside an object, then progress into another one in contact with the first one, and so on. Each object can resitute the vibration by vibrating itself. As example, when you talk to someone through a simple window, the sound of your voice vibrates in the air, then the air hit the window, then the window vibrate and transmit your voice through the outside air, which will be recieved by your listener. He hears your indirect voice.
Sound insulation
Sound insulation is not the same than heat insulation. The second is quite simple, and may have questionable results on sound. Otherhand, a good sound insulation is always an excellent heat insulation. A total sound insulation needs heavy implementation, very expensive most of the time, pervection is close to be impossible. Let's rather talk about sound reduction, which is much more reachable.
A good sound insulation is focused on three axis :
Prevent propagation through solids
Limit air propagation
Sound absorbtion (quieting)
1/ as sound may travel through solids, the goal is to lock the vibrations inside the solid. The method is simple : isolate the solid from others objects, with an antivibratory base or an antivibratory suspension.
2/ now we may limit air propagation. Another simple method : create an antivibratory environment within sound will be trapped. Generaly soft surfaces.
3/ Absorbant surfaces, like foam or mineral whool, can absorb vibrations by division. If the surface and path is large enough, a spectacular sound reduction can be conducted.
Note it's easy to reduce medium to high frequencies. Low frequencies needs more mass and surface to be reduced. If you have to manage low frequecies, better look at a way to limitate their early propagation/generation.
This are general principles, not a sound insulation bible. ;)
Quieting a Vacuum system
At last, we're ready to give an application of the above.
First, the best way to manage noise is to avoid creating some. So, a simple electric relay will make the vacuum start simultaneously as the MM spindle. No vacuuming needed ? No vacuum noise...
http://giemastruc.free.fr/Forums/VacuumIsolation.png
Second, think "box in a box", open space, means propagation (dust, smell, noise...). The best way to manage propagation is to manage environment.
It is right for a vacuum system, right for a MM, even if it takes more place and you may think about comfortable access to the machines. Think you don't have to access the vaacum tray frequently, and the MM can cut for a long time within your close presence.
Note the care needed to isolate in/outs (tubes, cables). Through, the noise trapp's path needs to be as long as possible for a better noise reduction.
About 's'.
'S' is a surface value in mē, needed for a good air flow.
Air flow can make noise by itself. It would be pittyfull to add noise while reducing some...
'S' is calculated from air speed (must be inferior than 20km/h to avoid grid whistling) and air flow.
The calculation is :
Air flow (m3/h) / 20 (km/h) / 1000 = grid surface and noise trapp section (mē)
I wish my english was good enough to make this topic helpfull for members.
I'll try to awnser any question.
Regards.