When blocking sound from travelling through a wall or between floor the insulation is only part of the answer. There are 3 types of sound to consider
This is sound that travels through the hard surfaces transferring from one surface into the next surface. An example of this is a person walking on a first floor wooden floor and the clomping sound being heard in the room below. To tackle this problem the 2 most effective areas to address are
Regular sounds travel through surfaces
This is the sound that will travel through the wall lining through the wall cavity (echoing if it in empty) and then through the next wall lining into the adjoining room. Another example is the sound from speech or a radio travelling through the first storey floor, bouncing around the cavity before coming through the ceiling on the other side. Another example is room inside the garage for someone to practise the drums or a sound recording studio where sounds from outside the recording studio need to be kept out of the room. For each of these situations we suggest you download the Gib Noise control systems book on how to create different levels of sound barriers on the wall linings. In each case the wall cavity needs to be filled to prevent sound that does get through from echoing withint the cavity.
When comparing sound products to be used in a cavity like a ceiling or wall cavity there are 2 measures you could look for to help decide which product you wish to select.
When working with this type of sound try to think of sound as water that can travel in any direction and is not limited by gravity. It can travel through all surfaces but the more dense the surface the weaker the sound becomes as it travels through it. This sound will also only be as good as its weakest point. eg. it is no good making a very soundproof wall with a regular window or hollow core door next to it and the sound will simply travel through this instead. Sound will also travel down pipes, through lightfittings and powerplugs so if youe going to soundproof a room do you homework to ensure the same level of sound reduction is applied to every surface.
Echo or reverberation
The third type of sound you may be treating is echo or reverberation. Once you have built the band practise room with all effort going into stoppping the sound escaping to the neighbours, you will find that the sound within the room is actually unbearably loud and not nice to listen to. The brand new home or restaraunt with all the sleek hard surfaces get just a few people in them and become loud and uncomfotable to be inside. The person accross the table is difficult to understand. This type of sound problem is called reverberation or Echo and needs a surface treatment product with a high NRC rating. Where an NRC of 1 is a solid surface that reflects all sound that hits it in various directions. The listener not only hear the person across the table talking directly at them, but also the speach bouncing off the various walls and a ceiling at the same time or milliseconds later in the form of an echo. An NRC of 1 is asoft panel that reflects all sound. If you have ever been in a hearing testing room where all sound dissapears as soon as it is made this is an NRC of 1. Gib has an NRC or 0.1, suspended acoustic ceiling have an NRC of 0.5-0.9. Specialist surface treamentfoams and pads have an NRC of 0.8-1 and are applied to an area of the walls an ceilings to recude the reverberation and make the sound easy and pleasant to listen to. Curtains, carpet, drapes, people, furnishings all help to increase the NRC and reduce the echo. Try this reverberation calculator and see what a difference various treatments can have. Each of these treatments is not achieved through insulation in cavities but other products applied to the outer surface of floors, walls and ceilings. Please call us on 0800 206 2879 to run through your sound situation and let us recommend and quote some improvements.
There is a lot of information here. In many cases it is best simply to call us on 0800 206 2879 and descibe the sound situation that you would like to create. We are not qualified acoustic engineers however have been designing acoustic systems for nearly 15 years and involved in ongoing research and development.