I. INTRODUCCIÓN

Un estudio de grabación se divide en dos secciones: Sala de Grabación y Sala de Control. Además del equipo adecuado se requiere de un tiempo determinado de reverberación (reverberation time –RT), una adecuada difusión del sonido, un aislamiento del ruido externo y un aislamiento entre las salas. En el proceso de diseño se hizo un recorrido por diferentes estudios de grabación en el país, encontrándose que un alto porcentaje, no tiene bases científicas ni cumplen los requerimientos acústicos, sino que enfocan su diseño en alguno ya construido. Muchos de los estudios de grabación son diseñados por músicos, dando las características acústicas que ellos creen agradables a sus oídos. Las salas de grabación de empresas importantes, cuentan con el diseño adecuado. Con el buen diseño acústico de este estudio de grabación, se busca obtener los mejores resultados a la hora de la grabación, edición y mezclas de cualquier producción musical.

II. MODELO

El diseño del estudio de grabación está basado en la necesidad de dar una calidad competitiva a las grabaciones, así mismo, ofrecer una excelente imagen y ambiente, la cual forma parte también fundamental para el desarrollo del ejecutante durante su grabación. Se va a construir en un terreno con una superficie de 30m de largo por 16m de ancho. Consiste de una sala de control compartida para tres salas de grabación. La sala de control tiene basado su diseño en la tendencia LEDE[8] e incluye difusores RPG (Reflection Phase Grating) del tipo QRD

(“Quadratic Residue Diffusor”)[1], ésto para crear un campo sonoro más difuso.

Aproximadamente, la primer sala de grabación de aprox. 20m2, está enfocada a percusiones específicamente, debido a que, una percusión emite frecuencias de resonancia diferentes a las de una voz humana o instrumentos de aire y cuerdas, por lo tanto, es necesario una mayor absorción y tiempo de reverberación RT más controlado. La segunda, de 52m2 es una sala general con un grado de absorción y tiempo de reverberación RT medio, tanto para voces como para instrumentos.

Una tercera sala específicamente solo para voz con un RT corto mide 20m2.

En la tabla I, se muestran los tiempos de reverberación deseados para cada sala[1].

TABLA I

TIEMPOS DE REVERBERACIÓN DESEADOS

Tipo de Sala RTmid en seg.
Sala 1 (Percusión) 0,4 – 0,6
Sala 2 (General) 0,7 – 1,0
Sala 3 (Voz) 0,2 – 0,4

Sala de Control 0,2 – 0,4

Los muros tanto externos como internos, son dobles con un espacio de aire entre estos de 2cm., revistiéndolos con fibra de vidrio de 1 ½”, el cual nos servirá como aislante. [1,2,3]

III. ANÁLISIS DE PARÁMETROS.

En esta sección se presenta la técnica de análisis para la obtención de parámetros.

A. Reverberación

El tiempo de reverberación (RT) es el tiempo que transcurre (en segundos) desde que el foco emisor se detiene hasta el momento en que el nivel de presión sonora (SPL) cae 60 dB con respecto a su valor inicial (Figura 2).
Para controlar el tiempo de reverberación aumentamos la absorción, ademas, nos basamos en la siguiente formula para determinar dicho tiempo:

B. Absorción

Podemos definir la absorción como la energía que incide en un obstáculo y no es devuelta al medio de transmisión, sino que se transforma en calor. El grado de absorción se puede especificar como el cociente entre la energía absorbida y la

incidente:

C. Aislamiento.

Las pérdidas por transmisión indican la capacidad de una pared para no transmitir las ondas sonoras. Estas pérdidas dependen sobre todo de su masa por unidad de área, su rigidez y el amortiguamiento en el material. En las construcciones típicas, estas pérdidas varían entre 30 y 70 dB de tal manera que el aislamiento sonoro, consiste básicamente en dividir mediante barreras físicas preferentemente con cierres totales, el sector que contiene a la(s) fuente(s) sonora(s) del que se desea proteger. Se mide el aislamiento acústico en diferentes frecuencias, normalmente 100-3150 Hz. en normas ISO con la siguiente relación:

Se precisará un aislamiento mayor al recomendado en la norma NBE-CA88, donde el nivel de emisión de ruido recomendado es de 40 dBA durante el día, y 30 dBA durante la noche.

D. Difusores.
Consisten en una serie de ranuras paralelas de forma rectangular, de igual anchura y diferente profundidad. Cuando una onda sonora con una dirección cualquiera incide sobre una de sus ranuras, ésta se propaga por su interior siguiendo un camino paralelo a las paredes de la ranura hasta alcanzar el fondo de la misma.

Para el diseño de los difusores se siguió el sistema descrito por Peter D´Antonio (Journal of the Audio Engieneering Society, JAES, Vol. 32, n°4, de abril de 1984)[9]. Se utilizarán difusores RPG del tipo QRD, los que nos ayudaran a tener buena difusión sonora, desde 344 Hz hasta 8.6 Khz. Las configuraciones se muestran en la Tabla III.

TABLA III.

CONFIGURACIÓN Y GRADOS DE FRECUENCIA DE LOS DIFUSORES QRD UTILIZADOS

Modulo o Periodo:
fmax (Hz) fmin (Hz)
QRD 11 688 344
QRD 41 4300 430
QRD 19 7233 506
QRD 31 8600 1228

La secuencia de profundidades necesaria para conseguir que dicha distribución de energía reflejada
sea lo más uniforme posible (en todas las direcciones del espacio y por tanto, que el difusor QRD
actúe efectivamente como tal), se obtiene de la siguiente expresión:

Sn=n2 mod p (5)

donde:
p=numero primo (3, 5, 7, 11…)
n=numero entero que va desde 0 hasta p-1
mod=operación matemática módulo.

IV. EXPERIMENTO

Se construyó una sala de dimensiones mucho más pequeñas que el propuesto (26.4m3) construido
de ladrillo y con piso de madera. Está ubicada en una avenida muy conflictiva en cuanto a transito
vehicular, donde el nivel de SPL llega a tener hasta 81dB. El tiempo de reverberación medido en el
recinto vacío después de hacer 10 veces la medición, apoyados de un sonómetro y promediando fue:
RT 2.2 seg. Matemáticamente se obtuvo un resultado de RT = 2.0 seg. Esta diferencia entre
resultados es dada por el grado de absorción de los materiales que citan algunos autores, que no
siempre será igual, debido a que no siempre son construidos de igual forma y con las mismas
características de densidad y masa. Entonces, podemos saber que la absorción total del recinto, dado
por la fórmula de Absorción total, teniendo 4 muros de ladrillo, piso de madera y techo de cemento.
fue de Atot=2.124 (ver Tabla 3)
TABLA IV. RESULTADOS DE ABSORCIÓN DE LA SALA ANTES DEL AISLAMIENTO

Dada la mala ubicación de este local, buscamos tener un aislamiento con un nivel máximo de 30dBA. Usamos la solución del tipo masa-resorte-masa, que no es otra cosa que combinar estructuras rígidas con absorbentes en medio, de forma que con mucho menos espesor y peso, mejora el grado de aislamiento (ver Figura 3). Se construyó un muro con madera de 3cm., seguida de una cámara de aire. Para evitar que en el interior de la cámara aparezcan ondas estacionarias que tiendan a acoplar los dos elementos simples, colocamos fibra de vidrio de 1 ½” con coeficiente de absorción de 0.8 como resorte, y que a su vez tiene excelentes características de amortiguamiento acústico. De esta forma, el sonido se disminuye hasta casi su desaparición. La pared de ladrillo va cubierta por una capa de poliuretano de 4cm seguida de una capa de fibra de vidrio también de 1 ½ “.

Los resultados obtenidos antes y después del aislamiento fueron los siguientes:

Antes del Aislamiento
SPLmax exterior= 89dB
SPLmax interior= 64 dB
Aislamiento total= 26dB
Pérdida de transmisión TL= -14.149 dB

Después del Aislamiento
SPLmax exterior= 89dB
SPLmax interior= 34 dB
Aislamiento total= 55dB
Pérdida de transmisión TL= -17.40 dB

Una vez llevado a cabo el aislamiento se midio 10 veces el tiempo de reverberación y su media fue: RT 0.4 seg
Matemáticamente ya obtenida la absorción total dentro de la sala (ver Tabla V), que es de Atot= 73.85 obtuvimos un tiempo de reverberación RT= 0.353 seg.

Acoustic-X™ is software developed to assist in the optimization process of small-room acoustics. Its goal is to provide users with information that will allow them to make correct and intelligent choices to improve the sound quality of their space. In order to achieve this goal, Acoustic-X™ uses several software modules, each dedicated to individual acoustic calculation tasks. Reviews accissible via this site.
http://www.pilchner-schoustal.com/old/a … ftware.htm

Reflex Software: http://www.mjm.qc.ca/en/reflex.html

CARA SOFT: http://www.acousticsoftwarereviews.com

AURORA – Software auralisation on PC
Aurora is a suite of plugins for CoolEdit: the room acoustic impulse response can be measured and manipulated, for the recreation of audible, three-dimensional simulations of the space.
http://www.ramsete.com/Aurora/

Acoustic Software Resources 1
An extensive collection of liks to acoustics and audio software.
http://www.ecgcorp.com/velav/vldocs/software.html

Acoustic Software Resources 2
Some Audio, Acoustics, Circuit Board design and other links
http://staff.niagara.edu/mls/softsor.html

Acoustic Software Resources 3
Several additional links to all branches of Acoustic Software. However most can be found via Acoustic Software Resources 1.
http://www.scientific-computing.co.uk/a … ftware.htm

Audio Toolbox Plus – TerraSonde
This is a hybrid of equipment and software. This equipment and software has won some Awards
http://www.terrasonde.com/

AudioTester (Shareware Eur 33.45, USD 28)
audiotestsystem: spectrumanalyzer,wavegenerator and oscilloscope with a soundcard.
http://www.sumuller.de/audiotester/

BEASY Acoustic Design
Professional software: Noise control and reduction, Architectural Acoustics, Environmental Acoustics, Sound propagation through sound absorbing materials, and much more.
http://www.beasy.com/products/acousticdesign/index.html

CARA 2.1 PLUS ($49.95 US Dollars )
The Windows software for audio and home theater enthusiasts! CARA calculates the acoustics of your room with 3D modeling of your sound room, loudspeakers, and listener locations. A test CD is also available at $19.95 or as total package at $64.95
http://www.rhintek.com/ e

CATT-acoustic
This is professional room-acoustic software. Also has FIReverb suite. Expensive
http://www.catt.se/ e

CLARA (ca 350 Euros)
Saint-Gobain Acoustic Comfort Software (Saint-Gobain Isover/Saint-Gobain Glass). Select and evaluate acoustically different construction systems which meet the requirements of European comfort classes.
http://www.isover.com/gb/frameset.asp?b … rubrique=5

CLIO electrical and Acoustical tests
PC-based system for electrical and Acoustical measurements. CLIOwin implements three different measurement techniques: MLS (Maximum Length Sequences), Sinusoidal Sweeps and FFT Averaging.
http://www.mclink.it/com/audiomatica/clioman.htm

COMET Acoustics Software (Professional = expensive)
Collins & Aikman Launches COMET 5.0 Acoustic Software. COMET is a computational simulation tool for comprehensive vibration and acoustic prediction for the automotive, aerospace and other high tech industries. COMET utilizes various analytical techniques to accurately predict the transmission, radiation and scattering of acoustic waves and their interaction in a variety of media including fluids, foams, and solids.
http://www.colaik.com/default.asp

EASE v3.0 for Windows
EASE v3.0 is an acoustic simulation software program designed for the Windows operating system that provides sound system designers an invaluable tool for predicting the performance of a sound system in a given venue. The software program is primarily geared toward large-room acoustics (churches, stadiums, arenas, theaters, etc.) and includes numerous acoustical design and analysis tools for Contractors, Engineers and Acoustical Consultants.
http://www.jblpro.com/ease/

ETF 5 (MLS software) – Acoustisoft (ca 150$)
ETF software is a highly accurate PC based acoustic measurement system designed to meet the needs of both hi fi enthusiasts and professionals. Two channel MLS measurements provide accurate results with even low cost standard pc sound cards.
http://www.etfacoustic.com/index.html

Fluidyn acoustic software
Professional software for environmental and room acoustics.
http://www.fluidyn.com/Home/Index_Home.htm

HpW-Works the Measurement System (69 – 300$)
HpW Works is a complete software based measurement system for the Intel HW platform. Analyzes a DUT using a sound card, wave files and text (ASCII) files. Various signal analysis are performed like RMS, DR, THD, THD-N and more. Check the customer list.
http://www.hpw-works.com/

INSUL Marshall Day acoustics
INSUL is a quick and accurate tool for predicting the sound insulation of walls, floors and ceilings. Price ca 1000 $
http://www.insul.co.nz/

MLSSA Acoustical Measurement System
MLSSA is the industry standard loudspeaker measurement system and the MLSSA Speaker Parameter Option (SPO) is the industry standard for measuring the Thiele-Small parameters of loudspeaker drivers. MLSSA and SPO both include QC (Quality Control) PASS/FAIL functions for high-speed automated production line testing of loudspeakers and drivers. Other important applications of MLSSA include speech intelligibility measurements according to IEC 60268-16 via the Speech Transmission Index (STI) and Rapid Speech Transmission Index (RASTI) as well as room acoustics measurements according to ISO 3382. For details, see the MLSSA Acoustical Measurement System and MLSSA Speaker Parameter Option brochures on the site..
http://www.mlssa.com/

NEMPEE Acoustics Software
a tool for acoustics engineers and architects to assist in providing maximum acoustical performance in building design. For example, an auditorium requires a specific design in order to reflect sound. This program can set up everything precisely and generate reports on the acoustics of a room. It considers surface area, building materials, and volume.
http://www.nempee.com/AcouSoft.htm

Nicolet technologies
Some professional, presentation and analysis software, also have hardware.
http://www.niti.com/software.html

ODEON – Room Acoustics Software
Professional program (expensive). This site includes lots of interesting publications in .pdf format. August 2001 an agreement has been made with Brüel & Kjær to become worldwide sole distributor of ODEON.
http://www.dat.dtu.dk/~odeon/

PC Audio/Visual Technical Web Site. VERY GOOD LINKS
Audio Testing-Related Hardware and Software Links. It lists the most common acoustic programs, known in the Audio, Studio world. Also includes tests on sound cards.
http://www.pcavtech.com/links/index.htm

Ramsete in 3 editions (Lite, Classic & II)
Room acoustic modeling – Ramsete is the first publicly available software based on the Pyramid Tracing computing scheme, which is quite different from traditional Ray Tracing or Cone Tracing schemes.
http://www.ramsete.com/

SEAM acoustic and vibration prediction software
Cambridge Collaborative’s SEAM software provides a methodof analysis that is particularly well suited for studying the dynamic response of complex structures at high frequencies. SEAM is used to predict interior noise and vibrationin aircraft, automobiles, and construction equipment cabs as well as the radiated noisefrom ships and the vibroacoustic environments for spacecraft. Other applications includemachinery noise, industrial noise, and building acoustics.
http://www.seam.com/

SIA Software – Smaart Live & Acoustic Tools
SmaartLive provides a practical and affordable PC-based implementation of a dual-channel FFT analyzer designed specifically for audio professionals. Acoustic Tools include lots of possibilities.
http://www.siasoft.com/smaart.html

SOPRAN (SOund particle Programme for Room Acoustics and Noise immission)
developed at the Fraunhofer Institute of Building physics IBP, allows the room acoustic design of auditoria (concert halls, theatres, multipurpose halls) and workplaces (factory buildings, open-plan offices).
http://www.ibp.fhg.de/rata/en/sopran-e.html

STx – Austrian Academy of Sciences
There is a FREE Real Time Analyser and a Trial version of STx itself. STx is the Windows version of the well-established S_TOOLS workstation for acoustics, speech and signal processing, which was first developed under DOS using the AT&T DSP32 signal processor card. STx now runs on 600 MHz PC systems equipped with Accelerated Graphics Port (AGP) cards and standard sound cards.
http://www.kfs.oeaw.ac.at/software/stx_download.htm

Sample Champion – PureBits (ca 100 – 500 Euro)
Professional Software Tools Audio Analysis and Processing. Sample Champion is an accurate and easy to use audio measurement software. It has been designed for acoustical technicians, sound engineers, scientists and students. With this software you’ll be able to easily perform Impulse response measurements, FFT analysis and much more.
http://www.purebits.com/index.html

Speaker Workshop FREEWARE
Speaker Workshop – test and design your own loudspeakers
http://www.audua.com/

Spectra Series software – MLS software - ST SPECTRA Sound Technology
SpectraLab, SpectraPro, SpectraPlus, etc. Several programs available in in different price ranges. The side also includes acoustic Test and Measurement PC based hardware and equipment.
http://www.soundtechnology.com/download-center.htm

Spectrafoo for MAC computers – Metric Halo Labs
SpectraFoo provides standards-based level metering, high-speed, high-resolution spectral analysis, the unique Phase Torch, correlation metering, triggerable waveform display, power balancing and a variety of power, envelope and spectral histories and phase analysis on any number of input or output channels. The SpectraFoo range is absolutely essential for broadcast and critical mixing & mastering.
http://www.mhlabs.com/products/

Spectrogram v 5.0.8
FREEWARE: Spectrogram can provide either a scrolling time-frequency display or a spectrum analyzer scope display in real time for any sound source connected to your sound card. Spectrogram allows unlimited recording and playback of the sounds from the audio spectrum display and can provide very high resolution spectrum analysis of wave files with a wide choice of frequency bands and frequency resolution and either linear or logarithmic frequency scales.
http://www.hitsquad.com/smm/programs/SPECTROGRAM/

Spectrum Analyzer v2.0 BETA FREEWARE
This small program is intended to measure the frequency response of a listening room with the aid of a regular computer. It records short sound sequences, performs a FFT then displays a cute diagram. The site also includes: Implementing Reverberation Algorithms with Matlab. These files are dedicated to the generation of artificial sound reverberation.
http://homepages.spider.lu/holzem/#

Steve Ekblad’s Free Audio Software Page + On-Line Audio Tools
A huge list of interesting things. Thanks to several manufacturers for providing a valuable resource for the hobbyist by providing these programs for a no-cost-trial [read shareware or demo] to the end user or in some cases totally free of registration fee requirements [freeware]!
http://www.wssh.net/~wattsup/audio/

The PC AV Tech Brings You:
Here is a web site built using CoolEdit and SpectraLab to perform technical tests published on the site.:
http://www.pcavtech.com/index.htm

ULYSSES Acoustic Design and Simulation Software – ca 1000$
ULYSSES© was developed with the intention to be a very fast, precise and really easy to use acoustic calculation, simulation and sound system design tool for our own consulting business. It features true 3-D CAD-based calculation, simulation and design routines for room acoustics and sound system design.
http://www.ifbsoft.de/

Visual Ears – KB Acoustics (ca 95 $)
Visual Ears, is an easy to use computer program that, through mathematical simulation, will help you find a “listening sweet spot” which minimizes the effects of standing waves (20-200Hz) and boundary reflections (20-500Hz). Visual Ears can handle rooms with sloped/cathedral ceilings and accomodates most speaker designs including sub/satellite systems. Read also the linked pages to the very positive test reports in Soundstage en Audiophilia magazine
http://www.kbacoustics.com/visualears/index.html

WinMLS – software for acoustics, vibrational & audio measurements
When visiting the site, you’ll see no typical commercial site, but this is professional software. Is available in cheap lite until professional expensive versions. Look at the Links page for references. Note from Eric: MLS measurement methods can have extreme advantages for insulation measurements by excluding background noise (equaling extended dynamic range).
http://www.nvo.com/winmls/door/

Dirac Catt Ulysess Arta

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El Monasterio de El Escorial es un singular complejo multifuncional, monacal y palaciego, según el paradigma de la Traza Universal, implementado por Juan Bautista de Toledo, que dio origen al estilo herreriano.

En El Escorial, la galería de susurros se llama la Sala de los Secretos. Es una de las variantes de las galerías, estas salas son mayores y el sonido va de un foco sonoro a otro al reflejarse sobre las superficies del recinto.

Se encuentra en la parte oeste del edificio, en la entrada noble llamada la antigua portería. Dicha sala es famosa porque parece ser que en ella se oían las confesiones que las reinas hacían en otro lugar del recinto.