Abstract: An acoustical panel has a multiplicity of short micro-slits, about 10 mm in length each, with each micro-slit having a wedge shaped cross-section in which the opening on the front side of the panel is wider than the opening on the rear side of the panel by a factor of about 2 to effectively absorb sound frequencies in the range of 250-2000 Hz, with the micro-slits greater than 4%. The micro-slits are spaced apart less than 5 mm and several different patterns of micro-slits may be employed including micro-slits that are straight as well as arcuate or some combination of straight and arcuate. The area of the micro-slits on the front surface of the panel exceeds 4%.

Abstract: A room acoustic diffuser exploits interference, by reflecting waves out-of-phase with the specular energy, making it possible to diminish specular energy. This is achieved by using a diffuser based on a ternary sequence, which nominally has reflection coefficients of 0, ?1 and +1. A method for obtaining the design sequence for Quaternary diffusers is also disclosed. Also, design methods for forming the sequences into arrays, and forming hemispherical diffusers are explained.

Abstract: An extended bandwidth folded well diffusor extends the diffusion bandwidth of a shallow, asymmetric diffusor by incorporating maximum-depth, folded L-shaped, half-width wells on both ends (sides) of a diffusor, thus providing increased maximum well depth without increasing the physical depth of the diffusor. When the inventive diffusor is placed in an array, the folded L-shaped, maximum-depth, half-width end wells form a novel T-shape, which offers a favorable impedance lowering the resonant frequency, thus extending the diffusor diffusion bandwidth. T-shaped recesses may also be located within a single diffusor. The front surface of the diffusor may be flat or curved or angled.

Abstract: Embodiments of aperiodic tiling of a single asymmetrical diffusive base shape employ welled or stepped one-dimensional or two-dimensional diffusors, a single or compound curved surface, or an aperiodic geometrical form. Surfaces are tiled in any orientation offering an unlimited number of tiling patterns. In the preferred embodiments of the present invention, a smooth transition between adjacent “tiles” is achieved. Using a single tileable asymmetric base shape reduces the number of shapes requiring manufacture while allowing modulation. The present invention even contemplates extending the inventive techniques into three-dimensional shapes to form volume diffusors. The technique employed to design diffusors to be used in accordance with the teachings of the present invention may rely upon visual appearance, a random sequence, a number theory sequence, or use of an optimization program.

Abstract: Embodiments of aperiodic tiling of a single asymmetrical diffusive base shape employ welled or stepped one-dimensional or two-dimensional diffusers, a single or compound curved surface, or an aperiodic geometrical form. Surfaces are tiled in any orientation offering an unlimited number of tiling patterns. In the preferred embodiments of the present invention, a smooth transition between adjacent “tiles” is achieved because the perimeter of each tile, where necessary, is provided with a specific depth and gradient whereby when adjacent tiles are placed in adjacency, there is a smooth transition between the adjacent tiles. Using a single tileable asymmetric base shape reduces the number of shapes requiring manufacture while allowing modulation. The present invention even contemplates extending the techniques thereof into three-dimensional shapes to form volume diffusors.

Abstract: An existing diffuser is modified by creating through-holes in its diffusive surface that allow sound to travel through the diffuser to the rear of it where an absorptive material is provided. The absorptive material may be made of any suitable material such as fiber glass, foam or mineral wool. The cut-off frequency between diffusion and absorption may be “tuned” or adjusted by varying the total volume of holes made within the diffuser, and by determining the particular cavities (and their depths) that are chosen to be modified through the provision of holes. In each embodiment of the present invention, holes or slots are formed in a diffusive surface and such holes or slots form one component of a resonant absorber. The perforations can be any shape or size and by varying the perforation and cavity size, the inventive devices may be “tuned” to begin to absorb sound below a desired chosen frequency.

Abstract: A motorized and computer controlled TRIFFUSOR® acoustical treatment system includes a plurality of TRIFFUSOR® banks mounted in various locations within a listening room. Mechanical actuators such as gears and sprockets are employed to mechanically couple the individual units of each bank together. In the preferred embodiment, an electrical motor is coupled into the gearing so that rotation of the electrical motor results in indexing of the different faces of each TRIFFUSOR® unit to the three possible positions (absorptive, reflective or diffusive) facing the interior of the listening room. A programmable logic-controlled motor control unit is provided and programmed to coordinate activation of different TRIFFUSOR® banks throughout the listening space.

Abstract: An appropriate binary sequence is used to create an acoustical treatment surface having desired parts with reflective properties and desired parts having absorptive properties resulting in the net effect of partially diffusive, partially absorptive properties. A genetic algorithm is designed to search for optimal 1D and 2D configurations for the acoustical treatments. A genetic algorithm essentially mimics the process of evolution that occurs in biology and is a known mathematical technique. During the course of genetic optimization, the fitness of individual sequences for the desired purposes is calculated. A useful fitness function includes terms that optimize the desired percentage of reflectivity and absorptivity. Through use of genetically optimized binary sequences, a curved surface may be constructed and optimized to find the best shape to achieve even scattering. The curved surface produces a dramatic improvement in effectiveness of diffusion.

Abstract: A two-dimensional binary amplitude diffusor (BAD) offering both absorption and modest diffusion is disclosed. The invention consists of a flat-faced panel with a series of alternating reflective and absorptive regions or patches defined by a binary sequence consisting of zeros and ones with a flat power spectrum, such as the Maximum Length Sequence (MLS) based upon shift register theory. Combining regions of absorption and reflection in the manner described herein results in an effective combination of absorption and diffusion.

Abstract: Acoustical seating risers for indoor arenas are made of a plurality of pre-formed units of L-shaped cross-section. These L-shaped sections are mounted atop one another on a separate pre-formed foundation to provide a mounting platform for rows of seats and additional acoustical steps in the aisles. Each riser unit includes an integrally molded acoustical element having a slit and recessed chamber or a series of slits and recessed chambers designed to absorb low frequency sounds below 500 Hz, thus permitting balancing of the frequency response within that range. Riser units are assembled together in an overlapping fashion to form the sealed and slitted cavities and protect the recessed chamber or series of chambers from water or other contamination.

Abstract: Numerous embodiments of a nestable sound absorbing foam each including a reduced area of attachment to an adjacent wall surface and a variable depth air cavity to enhance absorption. The embodiments include various configurations of "one-dimensional" sine waves, saw tooth cross-sections, triangular and crown shaped cross-sections as well as square wave cross-sections and part cylindrical cross-sections. In addition, two-dimensional nested topologies with a variable depth air cavity are also described. In each embodiment, the major portion of the rear surface of the material which is to be attached to a wall surface is spaced as far as possible from the wall surface creating a variable depth air cavity to enhance sound absorption. When the rear air cavity is sealed, additional low frequency absorption is achieved by increased air flows through the foam material caused by the pressure gradient in the low frequency pressure zone.

Abstract: A two-dimensional primitive root diffusor includes a two-dimensional pattern of wells, the depths of which are determined through operation of primitive root sequence theory. A prime number N is chosen such that N-1 has two coprime factors which are non-divisible into each other. From the prime number, a primitive root is determined and, in the preferred embodiment, an algorithm is used to determine sequence values for each well. Each sequence value is proportional to the well depth, with each sequence value being multiplied by the design wavelength and then divided by 2N to arrive at the actual well depth value.

Abstract: Disclosed are a variety of structural acoustical cinder blocks including locking blocks which are intended to be assembled together through the use of mortar to provide a diffusor of desired shape and configuration. Each diffusor includes a plurality of wells, the depths of which are determined through the use of number theory sequences, such as, for example, the quadratic-residue sequence developed by Karl Frederick Gauss. The surface irregularities formed in the blocks are unique in that they provide a flat power spectrum and constant scattered energy in the diffraction directions. Each of the blocks including wells also includes a low frequency sound absorbing chamber. The blocks are installed such that there is a stacked bond on the diffusing face and a running bond on the structural rear face. If desired, a single block may be made which includes an entire sequence of wells and dividers.

Abstract: Disclosed are embodiments of structural acoustical cinder blocks including blocks which are intended to be assembled together through the use of mortar to provide a diffusor of desired shape and configuration. Each diffusor includes a plurality of wells, the depths of which are determined through the use of number theory sequences, such as, for example, the quadratic-residue sequence developed by Karl Frederick Gauss. The surface irregularities formed in the blocks are unique in that they provide a flat power spectrum and constant scattered energy in the diffraction directions. Each of the blocks also includes a low frequency sound absorbing chamber. As the blocks are installed, a structural stacked bond is formed on both the diffusor face and the rear structural face. If desired, a single block may be made which includes an entire sequence of wells and dividers.

Abstract: A performance shell is disclosed which includes a plurality of modular components which may be assembled together to surround a performing entity ranging from a single soloist to a full orchestra. Modular components may be added and subtracted as desired to adapt the size of the shell to the size and type of the performance entity. The structure of the invention includes a plurality of rectangular recesses each one of which is designed to receive an acoustical device such as a reflective device, a diffusive device or an absorbing device. By carefully arranging the locations of these various devices in the shell, the performers will be better able to hear themselves and other musicians resulting in a performance which the audience perceives as louder, being more rhythmically in unison, and containing better loudness balance between sections than would be the case without the features of the shell.

Abstract: The present invention relates to an acoustical diffusor device which is made up of a plurality of specially designed and shaped cinder or concrete blocks which may be assembled together through the use of mortar to provide a diffusor of desired shape and configuration. Each diffusor includes a plurality of wells, the depths of which are determined through the use of number theory sequences, such as the quadratic-residue sequence developed by Karl Frederick Gauss. These surface irregularities are unique in that they provide a flat power spectrum and constant scattered energy in the diffraction directions.

Abstract: The present invention relates to an acoustical diffusor device which is made up of a plurality of specially designed and shaped cinder or concrete blocks which may be assembled together through the use of mortar to provide a diffusor of desired shape and configuration. Each diffusor includes a plurality of wells, the depths of which are determined through the use of number theory sequences, such as the quadratic-residue sequence developed by Karl Frederick Gauss. These surface irregularities arenique in that they provide a flat power spectrum and constant scattered energy in the diffraction directions.

Abstract: Disclosed herein is an improved sound absorbing diffusor device wherein the surface designed to face the sound source includes a plurality of sound absorbing wells of equal widths but different depths separated by thin sound absorbing dividers. The depths of the individual wells are based upon the quadratic-residue number theory sequence which is used in acoustic design. The wells are covered with an open weave fabric adhered thereover which fabric is specifically chosen for its ability to allow sound to pass therethorugh to the wells and dividers. Tests performed on the inventive sound absorbing diffusor have revealed significant reduction in sound levels of reflected sounds over that which would accrue from a flat absorptive panel.