An array of adjustable sound sources

The present patent application for industrial invention relates to an array of adjustable sound sources.

Line arrays of sound sources are known, which are sound systems composed of a set of sound sources disposed in linear configuration. Such arrangement of sound sources allows for giving directivity to the sound field. Therefore, line arrays are very much used in practical applications and spaces such as theaters, stadiums, cinemas, conference rooms, etc., where dispersion of sound energy in areas outside the audience must be avoided to reduce reflections that may deteriorate sound quality and word intelligibility.

Over the years, different studies for development and implementation of line arrays have been carried out in order to optimize inclination of sound beam in relation to position of audience and increase perception of sound pressure level.

A very important aspect is given by the fact that the sound field emitted by line arrays of sound sources can be aimed in a specific direction using digital processing techniques. Aiming can be obtained without mechanical movements, thus allowing for situating the line array of sound sources parallel to wall, perfectly integrating it in the surrounding setting.

However, such an approach is impaired by limitations due to physical properties of system, which affect sound quality. In particular, line arrays of sound sources have a maximum operating frequency, beyond which correct overlapping of wavefronts is not guaranteed, with consequent generation of destructive interferences Such a maximum operating frequency of line arrays of sound sources depends on the distance between individual sound sources, i.e. upper cut-off frequency increases when distance between sound sources decreases.

Moreover, it must be considered that line arrays of sound sources generate a lobe-shaped sound beam. When operating frequency increases, width of lobe generated by line array is considerably reduced, thus leaving completely uncovered audience areas.

In order to obtain acceptable width of sound beam in the entire frequency range, and lobe configuration without destructive interferences, distance between sound sources of line arrays must be as small as possible. This involves the use of very small sound sources that produce sound pressure levels that are very low and unsuitable for use in medium-large sized spaces.

Therefore, in order to improve the performance of line arrays of sound sources, it is necessary to use many sound sources and consequently a large number of amplification channels, with inevitable cost increase.

A common solution is based on the use of compression drivers associated with waveguides, which generate a relatively constant sound beam with continuous isophase wavefront, and provide suitable sound pressure level also for larger spaces. However, said wavefronts have an extremely narrow sound radiation lobe at higher frequencies, which prevents the use of traditional digital processing techniques to control the radiation lobe. Moreover, the need to maintain a sufficiently wide sound radiation lobe requires the use of mechanical aiming techniques, with conventional arrays of sound sources, such as J arrays, arrays with progressive splay or curve arrays with constant angle.

While they provide very good control of aiming and width of sound radiation lobe, such non-linear configurations of arrays of sound sources impose strict limitations on the mechanisms of the system, resulting in difficult installation. Moreover, they have a very high environmental impact that makes their use impracticable in special architectural spaces, such as churches and theaters.

In such places, aesthetic impact is preferred to sound quality, and normally typical arrays of sound sources are used, which reduce the reproducible spectrum to language, with very low qualitative performance that is not suitable for musical reproduction. Said drawbacks are solved, at least partially, in the US 7,426,278, patent, which discloses a device of vertically aligned sound sources, wherein each sound source is adjusted with suitable inclination angle in such way to generate a wavefront with desired shape to obtain sound cover in the area where it is aimed.

However, such a solution is not very versatile. In fact, once the inclination angle of sound sources is determined, the array of sound sources is made and said inclination angle cannot be adjusted. Evidently, such a type of array with predefined inclination angle of sound sources is designed to be used in a specific space and cannot be modified for different settings.

The purpose of the present invention is to eliminate the drawbacks of the prior art, by devising an array of adjustable sound sources that is effective, efficacious, functional, practical, versatile, simple to use and adjust.

This purpose is achieved according to the invention, with characteristics listed in independent claim 1 .

Advantageous embodiments appear from the dependent claims.

The present invention solves the incompatibility between aiming of sound beam and reduced environmental and economic impact, without neglecting sound quality and sound pressure levels (SPL) for the most diverse applications.

The purpose is achieved by filling the gaps of arrays at high frequencies. An array of waveguides with compression driver is proposed, with special mechanism to allow for independent rotation of guides. A digital control system of acoustic emission lobe of various waveguides of the array allows for uniform behavior in the entire operating range, from medium frequencies to high frequencies.

The array of sound sources according to the invention allows for obtaining a high quality and high power system, with all functionalities of a traditional digital control system, but with rectilinear geometry- Moreover, it has very reduced depth, with low environmental impact and is therefore suitable for architecturally sensitive applications. The principle of the new aiming technique is found in the opening diagram of the sound beam produced by a waveguide, and in general of a directive source.

Said sources are very directive at high frequencies because of the special shape of the conduit that produces an isophase front with very limited vertical opening and wide horizontal diffusion angle. Said directivity feature, which can be easily seen when frequency increases, loses value at medium frequencies, especially in the proximity of the lower operating limit of compression drivers. For these frequencies, in fact, the length of the emitted wave is higher than the dimensions of the mouth of the waveguide. This involves a directivity loss of the sound source and therefore application of beam aiming techniques exclusively by means of mechanical aiming.

Therefore, the inventive idea is to use digital aiming for medium frequencies, applying the necessary algorithms to incline the sound radiation lobe and check its width, and to take advantage of the directivity features of waveguides at high frequencies, in order to produce a front that is practically free from interferences, using mechanical aiming, hence, the definition of mixed aiming of the new technique that is the object of the present patent.

The two aiming techniques, i.e. mechanical and digital, combined in the same array are naturally interconnected and linked by constraints determined by the virtual structure given to the array.

Further characteristics of the invention will appear evident from the detailed description below, which refers to merely illustrative, not limiting embodiments, as shown in the enclosed drawings, wherein:

Fig. 1 is a perspective view of an array of adjustable sound sources according to the invention;

Fig. 2 is a side view of the array of Fig. 1 ;

Fig. 3 is an enlarged view of a detail of array of Fig. 1 ;

Fig. 4 is a perspective view of a waveguide of array of Fig. 1 ;

Fig. 5 is a sectional view of waveguide of Fig. 4;

Fig. 6 is a front view of waveguide of Fig. 4;

Fig. 7 is an axial sectional view along vertical plane VI I- VI I of Fig. 6; Fig. 8 is an axial sectional view along horizontal plane VIII-VIII of Fig.

6;

Fig. 9 is a perspective view of a sound source comprising the waveguide of Fig. 4 and a compression driver;

Fig. 10 is a side view of Fig. 9;

Fig. 1 1 is a side view of a wall portion of array frame, showing manual adjustment of position of sound source.

Fig. 12 is a perspective view of a second embodiment of means used to adjust inclination of sound source;

Fig. 13 is the same view as Fig. 12 taken from a different angle.

Fig. 14 is a vertical sectional view of array of Fig. 1 , wherein all sound sources are adjusted with axis laying on horizontal plane;

Fig. 15 is the same view as Fig. 14, wherein sound sources are progressively inclined with respect to horizontal plane;

Figs. 16 (a), (b) and (c) show arrangements of sound sources in vertical array without inclination of sound sources, with inclined array, and with vertical array with constant inclination of sound sources, respectively;

Figs. 17 (a) and (b) show arrangements of sound sources with curve array with constant curvature, and with vertical array with progressive inclination of sound sources, respectively; and

Fig. 18 is a graph showing how a vertical array with progressive inclination of sound sources produces the same sound effect of a curve array with constant curvature.

Referring to the enclosed figures, an array of adjustable sound sources according to the invention is disclosed, being generally indicated with numeral

(1 )-

Referring to Figs. 1 , 2, 3 and 14, the array of sound sources (1 ) is a vertical array and comprises a parallelepiped frame (2) with front opening.

The frame (2) comprises two vertical lateral walls (20), where a plurality of sound sources (3) disposed in vertical array configuration is hinged. Sound sources are disposed in a line, one above the other, and the center of each source is aligned on a vertical axis. Advantageously, sound sources (3) are in number of eight.

The frame (2) may also comprise a vertical back wall (21 ), a horizontal bottom wall (22) and an upper horizontal wall (23).

Each lateral wall (20) has a front border (24) having sawtooth profile with triangular toothing. Each tooth (25) is shaped as isosceles triangle with vertex of 60° angle facing frontally. The number of triangular teeth (25) is equal to the number of sound sources (3)

Referring to Fig. 3, a hole (26) with horizontal axis is obtained in the vertex of the 60° angle of each triangle (25) formed in the front border of the lateral wall (20) for pivoting of sound sources (3).

On the lateral wall (20), in the proximity of the pivoting hole (26), a slot (27) shaped as arc of circle is obtained, with centre in the pivoting hole (26). Referring to Fig. 1 1 , a graduate scale (29) is provided on the external surface of the lateral wall (20), in the proximity of the curved slot (27), to indicate inclination of sound source (3).

On the lateral wall (20), in the proximity of the curved slot (27), a rectilinear slot (28) is obtained, being disposed on the bisector of the curved slot (27) passing through the pivoting hole (26).

Referring to Figs. 9 and 10, each sound source (3) comprises a waveguide (4) and a compression driver (5) of known type, not shown in detail.

Referring to Figs. 4 - 8, the waveguide (4) has axis of symmetry (X) that coincides with the axis of propagation of sound emitted by the compression driver (5).

The waveguide (4) comprises a tapered body (40) extending from a back circular flange (41 ) to a front rectangular border (42). The back circular flange (41 ) is used to fix the compression driver (5). For illustrative purposes, the back flange (41 ) has an inlet hole with diameter of approximately 1 .3-1 .7 cm; the side of the front border (42) is comprised between 7 and 5 cm and the length of body (40) is comprised between 6.5 and 8 cm. Referring to Fig. 7, the body (40) of the waveguide, sectioned with a vertical plane, has a truncated-conical shape with increasing diameter from back flange (41 ) to front border (42).

Referring to Fig. 8, the waveguide, sectioned with a horizontal plane, is provided with a cylindrical back conduit (43) in communication with a truncated-conical front conduit (44). The back cylindrical conduit (43) has a flared back end (45).

Referring to Figs. 9 and 10, the waveguide (3) has two lateral walls

(46) shaped as plates, disposed in vertical parallel position.

A first pivoting pin (47) laterally protrudes outwards from each lateral wall (46) of the waveguide, in the proximity of front border (42). The two pins

(47) are disposed on the same horizontal axis (Y) that orthogonally intersects the axis of symmetry (X) of the waveguide. The pins (47) are hinged in corresponding holes (26) of lateral walls of the frame. So, the sound source (3) rotates around the horizontal axis of rotation (Y).

From the central part of each lateral wall (46) a second horizontal pin

(48) laterally protrudes outwards, which is engaged in the corresponding curved slot (27) of the lateral wall of the frame. The second pin (48) is longer than first pin (47) and externally protrudes from frame to be manually actuated by operator to adjust the sound source. The curved slot (27) acts as guide for pin (48). The ends of the slot (27) act as stop for pin (48). The length of slot (27) is chosen in such way to allow for rotation of sound source by + 35° with respect to a horizontal plane.

In the back of each lateral wall (46) of the waveguide a grid of holes (49) is obtained to stabilize the position of sound source.

Referring to Fig. 1 1 , when sound source (3) is mounted in frame (2), the rectilinear slot (28) of the lateral wall overlaps the holes of the grid (49) of the wall of the waveguide.

By manually moving the pin (48) inside the curved slot (27) the operator can read the graduate scale (29) and adjust desired inclination of sound source (3). Once the desired inclination of sound source is obtained, the operator locks the sound source (3) in position, by inserting a fixing plug (S) in the rectilinear slot (28) of the frame and in the corresponding hole (49) of the grid of the lateral wall of the speaker.

The waveguide (4) has reduced dimensions and is able to maintain curvature of wavefront lower than lambda/4 for frequencies lower than approximately 15kHz.

The reduced dimensions of said waveguides are especially important, since they allow for achieving maximum inclination angles of the entire radiated lobe of approximately 35°, whereas the maximum difference angle between inclination of two adjacent waveguides is approximately 15°. Said angular values must be compared with maximum splay angles possible in traditional arrays of sound sources with mechanical inclination, which usually reach values of approximately 10°; therefore, the array of sound sources (1 ) achieves said reference values without any problem.

Advantageously, spacing between acoustic centers of waveguides (4) is 72 mm. Said spacing between acoustic centers makes it possible to digitally direct the sound beam up to frequency values of approximately 5kHz; beyond such limit, an array of vertically disposed directive sources tends to lose inclination imposed by digital processing, since lobes irradiated by individual sources are reduced and do not originate mutual overlapping used in digital inclination.

Lobes of individual sources tend to assume the direction of waveguide; therefore, by applying a mechanical rotation of the waveguides according to desired angles, it is possible to maintain inclination of sound beam of array aimed as necessary, also at high frequencies.

Whereas they operate as indicated at higher frequencies, said mechanical inclinations of sound sources are practically superfluous at lower frequencies, since the lobe generated by the array does not respond to mechanical rotation of sources and, therefore, digital processing is needed to control behavior at lower frequencies.

Referring to Figs. 12 and 13, a second embodiment of the invention is disclosed, wherein inclination of each sound source (3) is adjusted by means of a geared motor (M), rather than manually. In this second embodiment elements that are identical or correspond to those already described are indicated with same numerals, omitting a detailed description.

The geared motor (M) is mounted on a support flange (6) fixed to frame (2) of array. The geared motor drives into rotation a worm (60) that engages with a rotatably mounted toothed wheel (61 ) with horizontal axis of rotation, in support flange (6) fitted to frame (2).

A pinion (62) is coupled with toothed wheel (61 ) and has same horizontal axis of rotation, although with smaller diameter than toothed wheel (61 ).

The waveguide (4) has a back wall (7) provided with rack (70) having a substantially curved profile with radius of curvature centered in the first pivoting pin (47) of sound source. Pinion (62) engages with rack (70). So, by actuating the geared motor (M), the worm (60) rotates, driving into rotation toothed wheel (61 ) and pinion (62) that engages in rack (70), rotating sound source (3) around horizontal axis (Y) of pivoting pin (47).

Evidently, such a motorized system is especially advantageous because mechanical rotation of sound sources (3) is controlled via software in compliance with operating frequencies and inclination of sound beam determined digitally.

The two (digital and mechanical) aiming techniques of sound beam of sound sources (3) are mutually constrained by the desired behavior of array of sound sources. Because of the special control technique, in fact, it is possible to generate any type of lobe obtained from most popular configurations of line arrays (straight array, curve-array, J-array).

In fact, by arranging sources (3) straight (Figs. 14 and 16(a)), a straight array behavior is obtained, with traditional symmetric lobe aimed vertically with width depending on dimensions of array.

To incline the radiation lobe by a determined angle (θ), it is sufficient to rotate all sound sources by the desired angle (Θ) (Fig. 16 (c)), and apply suitable delays to sources by means of digital processing. The result is the same behavior as a line array mechanically inclined by the same angle (θ) (Fig. 16 (b)). To obtain a more complex structure, such as array with constant curvature (Fig. 17(a)), it is necessary to rebuild delays and angles from associated virtual structure (Figs. 15 and 17 (b)). Starting from virtual configuration, sources are given same inclination they would have in array with mechanical aiming, whereas delays for digital aiming are obtained from differences, indicated with letter (d), between positions of sources of virtual array along a horizontal plane (axis x) (Fig. 18).

So, a symmetric radiation lobe is obtained, which is practically identical to the lobe of a curve array, therefore with constant width given by angle (a) subtended by arc, and with direction according to bisector of arc (B).

Following the same methodology, it is also possible to obtain a J configuration, generating a symmetric lobe that directs more energy to extreme areas of audience area and reduces energy in closer areas, guaranteeing uniformity of sound pressure when distance from source increases.

Numerous variations and modifications can be made to the present embodiments of the invention by an expert of the field, while still falling within the inventive scope of the enclosed claims.