Acustica Applicata

acustica

Reflections treatment

The purpose of the treatment is to subtract energy from the early reflections, so that they reach the

listener’s ear almost inaudible or very weak. To achieve this it is enough to use an acoustic trap as high as the

speaker or at least as high as the listener’s ears, which should be exactly

in the reflection point. Bearing in mind the reflections involved, acoustic traps that act from 120Hz and

upwards (with the exception of the treatment of the back reflections) are sufficient. In most cases DAAD3, DAAD2,

are sufficient for a good treatment. In the presence of strong reflections, more powerful traps should be used

(DAAD 4). Like the treatment of the resonances, the treatment of the reflections can be made incorrectly if the

acoustic traps are not located in the early reflection points, instead they stay in points of late reflections (many

rebound off the walls) lack in energy. The reflections that reach the listener after the sound fusion period, or that

arrive weak are useful for a comfortable listening and they must not be destroyed. For this reason DAAD have one lobo

of their lateral surface more sound diffusing than the other .

lateral reflections

Recent studies have shown that the major part of correct sound reproduction is determined in that brief time-lapse which

follows the attack transient. That which comes in the first 25 milliseconds will determine some of the sound qualities

(focusing, tonal balance etc.); the time delay included between 25 and 60 milliseconds is determinant for the ambience sensations,

to project the listener in the recording sound dimension. The complicated acoustic events which happen within these two periods

determine approx. 70% of the final sound quality ( the remaining 30% depends on the quality of the direct sound meaning the sound

reproduction system).

 

ACOUSTIC STUDIO

The sharp distinction between tonal balance and musical articulation has been made mainly with teaching purposes.

In the daily practice you will see that if one improves, the other improves as well and vice versa.

We insist that:

1) the positioning of the speakers and the listening point especially affects the

tonal balance.

2) the acoustic treatment significantly improves the musical articulation.

but if you put a certain number of broadband acoustic traps into a room you will

see how the A.Q.T. graph, though maintaining constantly the value of the average

musical articulation, will change depending on the position of the traps in the room

itself; both the tonal balance and the position on the graph of the improvements of

the musical articulation will change.

 

PRACTICAL SOLUTIONS TO THE MOST FREQUENT PROBLEMS

Confused and resonant basses, acoustic slime

Cause:

Addition of resonances in narrow frequency areas. Decaying times in respect to the frequencies of the

warm zone are too long. Speakers too close to the corners or equidistant from

the lateral and back walls or too close to the back wall.

Solution:

Treat the resonances in the corners and where it is

necessary. Move the speakers away from the back wall or from

the corners.

confused

 

Harsh sound

Cause:

Excess of high frequencies caused by lack of low

range or by very strong back reflections (especially

when the listening point is a sofa against the wall) or

by fluctuating echo.

Solution:

Treat the back reflections and/or move the listening

point away from the back wall; put an acoustic trap on

the front and on the back wall exactly in their points of

orthogonal projection.

Draw the speakers up to the back wall.

harsh

 

Hole in the middle of the image, lack in focusing

Cause:

Too strong primary lateral reflections.

Listening point too near.

Solution:

Treatment of the lateral homolateral reflection and/or

the controlateral reflection.

Move the listening point further away.

hole

Room which saturates at low volumes, lack indynamics

 

Cause:

Excess of reverberation: in the room too much

resonant energy, which has not the time to fade, and

so persists.

Solution:

Acoustic treatment to obtain shorter decaying times,

that is to say faster, keeping the acoustics of the room

alive.

 

room saturns

 

Narrow image

Cause:

Lateral and back reflections being too strong.

Lack in treatment in the front corners.

Solution:

Treatment of the early reflections and of the front

corners.

narrow image

 

Unbalanced image

Cause:

Bad positioning of the system.

Bad acoustic treatment.

Solution:

Place the speakers in a way that the resonant front is

homogeneous.

Rebalance the differences with an appropriate acoustic

treatment different for the lateral reflections, trying to

re-establish an acoustic symmetry.

unbalanced