These programs let you view, and in some cases hear, acoustic simulations of a given sound system in any venue. Today there are numerous computer programs capable of predicting the acoustics of a venue; the best known are EASE, distributed by Renkus Heinz, and ODEON, distributed by Brüel & Kjær, although we could mention others such as CATT Acoustic, Bose Modeler, Epidaure...
These programs require a certain knowledge of physics and acoustics to get the most out of them. They began to be developed in the mid-1980s, although it wasn't until 1990 that they started to take shape as such. They let you view, and in some cases hear, acoustic simulations of a given sound system in any venue.
We need to know that, to run simulations, we have to enter as much data into the program as possible in order to obtain results as close to reality as possible. Hence the complexity of simulation, since we need to know all the dimensions of the venue, as well as those of any obstacles in it. Also the materials and shapes present in the venue, in order to take their absorption coefficients into account.
In other words, if we had to enter the maximum amount of data to make the prediction, it would be very difficult to use this type of program on any artist's tour, since at most, on some occasions, all we have is a reference for the place where the show is held, while on others the promoter may provide us with digital drawings in DXF format, the native AUTOCAD format.
As a curiosity, it is worth mentioning that there is an option on the Internet, the MIREM program, a database of performance venues in Spain, with everything from AUTOCAD drawings, photos and technical equipment to plenty of information about every venue. You can view it at www.sgae.es, or go directly to www.artenetsgae.com/mire/index.htm, which belongs to the Sociedad General de Autores de España (Spain's authors' society). I should mention that I have personally made predictions with drawings downloaded from MIREM and, on arriving at the venue, noticed some small variations compared with the drawing.
Simulating a loudspeaker
Both the acoustics of a venue and the propagation characteristics of a loudspeaker can be viewed perfectly, as we see in the simulation from the CLF program; depending on the file, the resolution will be 10º, 5º and 1 octave or 1/3 octave. We have taken Martin Audio's AM15 loudspeaker to look at its sound propagation simulation, as well as all its technical specifications.
In the CLF program used below, we see the cabinet's technical specifications; the resolution is 5º and 1/3 octave. In this case, the drawing at the top corresponds to the horizontal and vertical dispersion (SPL) plot at a frequency of 1KHz, viewed in 3D. Thanks to the software we were able to obtain a horizontal and vertical polar diagram, this time viewed in 2D, from which we obtain
- Imported DXF drawing
- Acoustic prediction result
- Focus
The rest of the information obtained concerns the anechoic chamber, measurement distance, input voltage, sensitivity and SPL at each frequency, impedance, horizontal and vertical coverage angles..., for each frequency, with the option of viewing all these characteristics graphically.
These are the main features available in this excellent program for the technical visualization of loudspeakers.
Simulating venues
We will focus on the EASE program, which is one of the best known, although this type of program is not the most practical for day-to-day sound reinforcement work, given its complexity and the lack of time engineers on tour have.
To partly solve this problem, almost all loudspeaker manufacturers have their own acoustic prediction programs, of varying sophistication.
Whereas most professional simulation programs describe the natural phenomena of acoustic propagation, EASE is geared more toward adapting a sound system to the acoustic properties of any given venue. Thanks to a database of loudspeaker characteristics from most manufacturers on the market, the user has access to most sound reinforcement systems.
* EASE screenshot* EASE screenshot
* Mapp Online screenshot
EASE uses a resolution of 10º in the polar diagrams for loudspeakers, in bands ranging from 125Hz to 8KHz (depending on the version).
The information for each loudspeaker is frequency response, relative level, directivity, sensitivity, impedance and maximum power. Although a cluster can be simulated, the calculation times would be very long, so it is sometimes better to use larger models in smaller numbers.
The program runs on Windows. From the very start, we see the basic functions of any acoustic simulation program, although the submenus do require studying the user manual. Simulating a venue is fairly quick, and a few minutes are enough to enter a hundred surfaces. There are automatic functions for symmetry and joining surfaces, as well as the option of importing drawings from DXF (AUTOCAD) files.
The algorithms used are based on spherical wave propagation. Ray tracing simulates reflections using image sources, a purely geometric calculation. The main drawback of this type of simulation is the considerable calculation time.
As for acoustic criteria, the first would be RT60 reverberation time, which can be calculated using the Schroeder method, more accurate than the Sabine method. There is a function that suggests to the user certain materials depending on the desired reverberation time. You can identify unwanted reflections and the exact place to put absorbent panels. There is also the option of applying an initial time delay (ITD), which lets you adjust delay times. SPL levels are shown in different colors, and constructive and destructive interference take phase into account.
EASE evaluates the C7, C50 and C80 intelligibility criteria, which correspond to the European critical distance. C7 is the ratio between the energy contained in the first 7ms and the energy measured in the interval from 7ms to infinity; C50 uses 50ms and is defined as the Alcons intelligibility index; and finally C80, where the time is 80ms.
Acoustic prediction programs created by loudspeaker manufacturers
To avoid complexity on tour and to get the best performance from their loudspeakers, most manufacturers have developed their own programs since the arrival of line arrays: L-Acoustics with Soundvision, Nexo with GeoSoft, Martin with ViewPoint, Meyer Sound with Mapp, Electro-Voice with EVLaps...
* EASE screenshot
Special mention goes to EASE FOCUS, a free general-purpose acoustic prediction program geared toward line arrays, which is "offered" to brands that don't have their own acoustic prediction program.
Although most programs are based on Excel spreadsheets and powerful macros, more and more manufacturers are now using better resolutions and including interference between cabinets.
We have chosen Mapp Online as an example, since it is one of the most powerful programs created by a manufacturer and one of the most veteran. Development of this acoustic prediction program began quite a few years ago. The program is free; you just fill out the request form on the manufacturer's website and within a few days you receive a personalized download link.
Another feature of this program is that it requires an Internet connection, which is easy nowadays with phones and the mobile data cards offered by national carriers. This outside connection is needed to connect to the lab Meyer Sound has in the USA, where all the calculations are done. All the loudspeakers are placed in the anechoic chamber and measured from the lowest to the highest frequencies; it is worth mentioning that this anechoic chamber has a telescopic arm identical to those used at NASA to grip the cabinet under test and rotate it 360º in steps of 0.1º.
* BOSE Modeler screenshot
All that database and all those calculations must be handled on the computers at those labs, with Mapp connecting as the "host," and for this the program is based on "Java." When you open the program, two windows appear, one for the sound field and the other for virtual simulation. The first is the main window, where the venue is drawn or inserted, and also where the sound system is inserted and configured. This window shows environmental parameters such as temperature, humidity... and is where you specify the frequency chosen for the prediction, as well as its bandwidth.
In the second window we get the virtual simulation of the system's frequency response according to the chosen measurement microphone and its position on the X, Y axes; in addition to the frequency response, we get the impulse response and the spectrum at the selected resolution, up to 1/24 octave.
In the top window we see how a line array has been placed with its respective angles to cover different, previously drawn zones in a theater. The colors indicate the SPL levels at the selected frequency, in this case 2KHz; on the left we have the color bar to see the degree of SPL attenuation. If we want to know exactly what the SPL level would be at a given point, we just place a measurement microphone at that point and run the prediction.
In the loudspeaker configuration window we can choose the angle of each cabinet, of the whole array or of the "top grid," also called the "bumper," which is the metal structure that supports the weight of the array. It is possible to choose the polarity, level and delay of each cabinet independently.
Another very useful piece of information in this window is that, when configuring our array, we get precise information on the different weights at the front and back, so we can anticipate the type of structure we need to choose to support the system. In addition, the latest version of Mapp has built-in parametric EQ parameters and filters from the powerful Galileo loudspeaker processor.
Finally, I want to stress the use of this type of program, since they are quite reliable, and let's not forget that the vertical coverage of line arrays is so narrow that an error of a single degree can leave some parts of the audience uncovered.
