Theoretical Considerations of Acoustics in Rooms – Acoustic Parameters and Time Criteria

As mentioned in the acoustic introduction to home theater, to create a home theater regardless of the shape and size of the space, we need to consider the best equipment with the best layout in space. To implement the above, we will explain the theoretical issues. To begin with, we have gone to the two sections of audio parameters and time criteria.

1. Room Acoustic Parameters

A room can be considered as an acoustical linear and time-invariant system. Therefore, an impulse response in the time domain, which determines the decay, gives you a complete description of a room. Various acoustical parameters are based on the impulse response of a room and address the relative energy content in given time intervals which will be shortly discussed.

2. Time Criteria

2.1. Reverberation Time

The reverberation time RT is defined as the time in seconds required for the sound level in a room to decrease by 60 dB from its original level after a continuous sound source has been turned off. This will be a change of one thousand or one million in sound pressure and sound intensity respectively.

This measurement refers to T60 but in practice smaller time intervals such as -5 to -35 dB T30 or -5 to -25 dB below the initial value are more reasonable and further extrapolated to obtain the decay of 60 dB.

The reverberation time is one of the most important quality criteria for the acoustical design of a room and is useful to predict in advance its acoustical behavior in simulation programs

2.2. Early Decay Time (EDT)

The early decay time (EDT) is obtained by evaluating the decay of the first 10 dB. Early reverberation contains the primary reflections which arrive within the Haas fusion zone. These reflections are perceived as being part of the direct sound and tend to reinforce the direct sound. The early reverberation also affects the clarity of sound, which increases with more energy comprised in the early reverberation and decreases, respectively

The EDT shows a better correlation with the reverberation perceived due to masking effects while running speech and music. The later and weaker part of the decay often gets masked by the next syllable or musical note.

2.3. Center Time

Similar to Clarity the paramter  Center Time t<sub>s </sub is also used to describe the balance between early and late arriving sound energy. It can be considered as the balance between clarity and reverberation which describes the center of gravity of the squared impulse response:

Low values of ts correspond to clear sounds, whereas higher values refer to the dominance of late and reverberant energy. The subjective difference limen for t<sub>s </sub is about 10 ms, and the expected diffuse field value can be given by:

T is reverberation time.

What has been said so far and what we will discuss in detail in the future, will pave the way for creating a home theater of the highest quality. The audio products offered in Saba Smart systems, which include Dali speakers, Yamaha amplifiers and inakustik cables with their great variety and high quality, make it possible to implement any type of equipment according to the relevant needs.

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