Home cinema acoustic & soundproofing design
One of the most important elements in bringing the true home cinema experience into your home, is perfecting the room itself. The way that sounds, both inside and outside the room interact with the room, will have a direct impact on the enjoyment the cinema delivers.
Sound proofing and acoustic treatments tackle different issues, in different ways, but are both important to maximising enjoyment from your new cinema.
One of the most common issues effecting a poorly designed home cinema is a lack of soundproofing, preventing you from using the Cinema to its maximum potential at the times you want to. This involves both containing sounds inside the room, but also preventing you from hearing sounds from outside.
We often want to turn the volume up to a level that convey a sense of excitement, with action sequences, gun fire or explosions requiring a suitable level to sound realistic, and transport us into the world of the movie. If the Cinema room, is located near to other living rooms in the house, or close to children’s bedrooms, it may not be practical to turn the volume up to the level you’d like without disturbing others.
Additionally, sounds entering the room from outside can destroy the illusion the film maker is presenting and our ability to suspend disbelief. We are very quickly taken out of the movie setting and right back in to our home if we hear familiar noises outside the room, including traffic or aircraft noise, wind & rain, or even family members in adjoining rooms.
Importantly, by making the Hime Cinema a very quiet room to begin with, we get the same dynamic effects at lower listening levels with the benefit of greatly increased audio clarity.
We calculate the required level of soundproofing for each room, using tried and tested methods which take up as little space as possible, maximising precious floor area.
The acoustic treatment of the room, allows the audio system to perform at its best. We want a neutral room, that allows the recorded ambience in the movie soundtrack to dominate. We are very good at judging a size of a room by the sounds that we hear, so If the movie is set in a large cave, an open field or a small office, the sound should reflect that, without giving away the size of the actual listening room.
Our approach to room treatment is two fold. Firstly, we must to reduce the effects of the direct reflections between the speakers and the seating position. This reflected sound, arriving later than direct sounds, reduces clarity and positioning of the sound.
Secondly, we want to reduce the time that sounds echo around the room. In a large concert hall, this would be measured by the time the reverberations take to decay by 60dB. We don’t really get true reverberation in a typical Home Cinema, but the measure of simple reflected sounds is equally valid for our needs.
The RdT60 (Reflected decay Time) becomes our Home Cinema measure of the duration that a sound is still audible after the initial sound impulse. There has been much Scientific research on the most enjoyable level of this audible reflection. If the room has too much absorption and the RdT60 time is very low the room will sound sterile and unpleasant to spend time in and conversation between guests will be difficult. If the room has too little absorption, each sound is masked by the continued echo or ringing of the sounds before, making it difficult to follow the dialogue or enjoy small details.
Generally an RdT60 under 0.2 seconds is too low and above 0.5 Seconds is too high. We calculate the ideal value based on the size of the room, as found by scientific research and publiushed by the International Telecommunication Union, in a research paper Rec. ITU-R BS.1116-1.
This formula gives us an RdT60 of 0.2-0.4 for rooms 25-250m3 .
Importantly, the decay time should be even across all frequencies. Historically, designers may have only planned the RdT60 at 500Hz, but this leads to very poor rooms, where the bass booms and dominates or high frequencies sound very unpleasant and tiring to listen to.
At Cinema Lusso, we calculate the required acoustic treatment from 63Hz to 8000Hz at every octave, only this way can we guarantee your enjoyment and the perfect listening experience. As we construct and calibrate the room, we fully test and measure this decay time, with our audio calibration reports confirming we have achieve our acoustic design goals.