WO2023237983A1

WO2023237983A1 - Directional acoustic louspeaker

Info

Publication number: WO2023237983A1
Application number: PCT/IB2023/055653
Authority: WO
Inventors: Alessandro TATINI
Original assignee: H.P. Sound Equipment S.P.A.
Priority date: 2022-06-08
Filing date: 2023-06-01
Publication date: 2023-12-14

Abstract

Directional acoustic speaker comprising a pair of mutually equal speakers (A, B; A', B') arranged symmetrically with respect to a common median vertical plane (V1) and on a same horizontal plane (P) at a height (Q) with respect to a walking plane (G), in order to emit a sound beam in said frequency range focused in a preferential listening area (S) adjacent to the speaker and with reduced lateral dispersion with respect to the median vertical plane (V1) orthogonal to the speakers (A, B; A', B').

Description

“DIRECTIONAL ACOUSTIC LOUDSPEAKER”

★★★★★★

Technical Field

The present invention relates to a linear directional acoustic speaker, in particular for broadcasting voice messages such as announcements and instructions addressed to an audience of people present in a preferential listening area.

State of the Art

Speakers consisting of a line of loudspeakers side-by-side, also called "line arrays", which behave as a single sound source and which are used to produce a uniform sound pressure of high value, have been known and widely used for a long time.

The linear speakers have, by their nature, a wide acoustic dispersion laterally to the plane containing the line of the loudspeakers, typically around 110-140° and a reduced dispersion on the plane containing the line of the loudspeakers, which typically varies from 10 to 15 degrees depending on the length of the speaker, the construction and geometric features of the loudspeakers, their orientation and the distance therebetween.

Suitably oriented, linear speakers are therefore an advantageous solution when the sound emission is to be directed in a preferential listening area such as an audience of people gathered in a room or a limited environment.

It is also known that the directionality of the linear speakers is marked for high frequencies, i.e., frequencies at which much lower wavelengths correspond to the physical length of the array, but is progressively reduced for the medium and low frequencies, for which they tend to have a much wider dispersion.

By way of example, for arrays about 50cm in length, high directional frequencies can be referred to for frequencies higher than 2000HZ, to which corresponds a wavelength in air of about 15cm.

The solutions of known type therefore have significant drawbacks when it is desired not only to delimit a listening area in space, but to optimize the sound diffusion in that area for medium-low sound frequency ranges of the human voice, approximately between 80 Hz and 2000 Hz. The currently known systems are particularly ineffective when the acoustic broadcasting to a horizontally limited area is to be concentrated in order to eliminate disturbances in adjacent areas, for example in the case of broadcasting voice announcements intended for passengers aligned along a railway track.

Object of the invention

The present invention is intended to provide a directional acoustic speaker which overcomes the drawbacks of the already known solutions and allows to specialize the acoustic broadcasting in the typical frequencies of the human voice and to focus it in a listening area at a privileged vertical height and with a limited horizontal amplitude to reduce the disturbances in the lateral areas.

Summary of the invention

These objects have been achieved by creating an acoustic speaker according to at least one of the appended claims, in which a pair of loudspeaker lines arranged divergent with respect to a common vertical median plane and on a same horizontal plane at a height with respect to the walking plane is provided so as to emit a sound beam optimized for the human voice, focused in a preferential listening area adjacent to the speaker and with reduced lateral dispersion.

A first advantage is that the acoustic emission is focused along a band of reduced horizontal amplitude, reducing the noise disturbance outside this area.

A further advantage is that the acoustic emission is focused on both medium- high frequencies and medium-low frequencies,

A still further advantage is that a high quality of sound can be achieved in the area of interest.

List of Drawings

These and other advantages will be better understood by anyone skilled in the art from the description below and the accompanying drawings, given as nonlimiting example, in which:

- fig. 1 shows a preferred embodiment of a speaker according to the invention applied to a support pole;

- fig. 2 shows a bottom view of the speaker of fig. 1 ; - fig. 3 shows a right side view of the speaker of fig. 1 ;

- fig. 4 shows a left side view of the speaker of fig. 1 ;

- fig. 5a, 5b schematically show preferred installations of multiple speakers according to the invention;

- figures 6a, 6b schematically show the diagram of the sound pressure in two preferred embodiment examples of a speaker according to the invention.

- fig. 7 shows a preferred installation example of the speakers according to the invention,

- fig. 8 shows in side view a further embodiment of the speaker, provided with a pair of opposite directional horns.

Detailed description

With reference to the attached drawings, a preferred embodiment of a directional acoustic speaker according to the invention is described.

The speaker comprises a pair of parallel mutually equal loudspeaker lines A, B, fed by a common signal and formed by a plurality of single aligned loudspeakers 1 , preferably eight loudspeakers 1 equally spaced for a total length of the line between 40cm and 60cm and equal, in the example described, to about 50cm, oriented in diverging directions with respect to the median vertical plane V2 parallel to the lines A, B.

In the described example, the lines A, B have a substantially straight geometry, but it is understood that more or less markedly curvilinear configurations can be provided depending on the specific application required and separate speakers or a common speaker can be housed.

In the described embodiment example, the modules 1 have an optimized frequency response for broadcasting voices in the frequency range 160 Hz - 20 kHz.

The lines A, B of the speaker are arranged on a same horizontal plane P at a height Q with respect to a walking plane G which is preferably adjustable and between 2 metres and 4 metres, in the described example equal to about 3 metres, and are supported by a pole 3 mounted on the walking plane (fig. 1 ).

Alternatively, the lines A, B can be supported by vertical suspension means 4, e.g., suspension chains from an upper vertical wall 5 (fig.7). With the solution adopted, by virtue of the horizontal arrangement of the lines A, B, the sound beam emitted by the speaker is concentrated in a preferential listening area S adjacent to the speaker at a height determined by the installation height Q and by the downward angle a of the loudspeakers 1 so as to correspond to the listening point of people standing along the direction defined by the median vertical plane V1 orthogonal to the lines A, B.

In addition, the listening area S is delimited laterally with respect to the median vertical plane V1 at an amplitude which depends on the listening distance from the speaker and the loudspeaker length of the same lines, in the described case equal to about 50 cm, thus reducing the perceived sound away from the plane V1.

Preferably, for installations at a height Q equal to about 3 metres, the lines A, B, or the individual loudspeakers 1 , are oriented to radiate in opposite directions and downwards with an angle a which can be adjusted with respect to a horizontal plane, preferably between 0° and 30°, for example 15°, and optimized to favour a listening height of about 1 .5 metres from the walking plane and to guarantee, thanks to the features of the loudspeaker lines A, B, a vertical dispersion V of about 90° and a reduced horizontal dispersion H, equal to about 10° (fig. 1 ).

The invention is particularly advantageous for applications in which it is desirable to obtain a marked prevalence of the sound pressure in one direction, and an attenuation of the sound in the orthogonal direction, such as in the case of speakers used along railway tracks and intended for broadcasting messages intended only for users arranged along the track.

By way of example, fig. 6a, 6b schematically show the sound pressure (SPL) obtained with a speaker according to the invention, which is strongly polarized along the median vertical plane V1 orthogonal to the lines A, B and reduced along the median vertical plane V2 parallel thereto.

Fig. 6a shows the SPL diagram obtained with a particularly advantageous embodiment of the speaker, in which the loudspeaker lines A, B of the speaker are fed with opposite polarity and are arranged at a mutual distance "d".

By virtue of such a solution, the medium-low frequencies emitted by the loudspeakers of the lines A, B, by their nature omnidirectional, being in reverse phase tend to be erased in the points equidistant from the lines A and B, or in the median vertical plane V2, while moving away from the condition of equidistance and in particular in the listening area distributed along the plane V1 orthogonal to the lines A, B, will undergo a lower attenuation thanks to the mutual distance "d", thus maintaining a better sound quality precisely at the medium-low frequencies of greater importance for broadcasting voice messages.

Furthermore, according to the invention, the speaker lines A, B are spaced apart by a mutual distance "d" preferably between 20cm and 40cm, in the described example 30cm, to which corresponds a minimum cancellation wavelength of 60cm and therefore a frequency of about 500Hz, which will result in the less attenuated frequency ensuring a better listening quality in the range of medium-low frequencies typical of the human voice.

With reference to figures 2-5, an embodiment of the speaker is described, in which the linear loudspeaker lines A, B are installed in a centrally perforated frame 7 with a seat 8 for the passage of a vertical pole 3 to which the speaker can be fixed at a height Q adjustable by means of clamping brackets 9.

Preferably, the frame 7 further comprises a lower bottom 10, an upper containment wall 11 of the lines A, B and upper side screens 6 inclined downwards and arranged protruding above the loudspeakers.

According to the invention it is also possible to provide both a single installation and a multiple installation of speakers, fed by the same signal and aligned along the median vertical plane V1 at a distance preferably between 20 and 30 metres, for example 25 metres, as schematically shown in figures 5a, 5b.

In the case of speakers with counter-phase fed loudspeakers (dipole configuration), it has been found that two different alternative installation modes can be advantageous, schematically illustrated in figures 5a, 5b, in which the loudspeaker lines A B in phase opposition can be installed in concordant mode, i.e., with loudspeakers with the same polarity which emit towards the listening area comprised between two adjacent speakers (case ABBA - fig.5a) or in discordant mode (ABAB - fig.5b) with loudspeakers in counter-phase facing each other.

In particular, it was found that in the case of two-to-two concordant ABBA polarity, a better coverage homogeneity is obtained in the intersection areas of the sound fields and a better intelligibility, but a lower lateral attenuation, while in the configuration with alternating ABAB polarity, there is a significant reduction in the overall signal level in the areas where the emissions of two adjacent speakers intersect but a greater attenuation in the lateral areas where the acoustic disturbance is to be reduced.

As the distance of the sources varies, changing the interference figure and thus the relationship between the levels and the intelligibility of the two solutions, it is also advantageously possible to choose the configuration which best adapts to the particular application.

Referring to figure 8, a further embodiment of the invention is described, in which in place of the pair of loudspeaker lines A, B, a pair of oppositely- oriented, directivity-controlled horn speakers A’, B’ is provided, mounted so that the distance between the respective acoustic emission centres is equal to one half of the wavelength of the lower limit of the loudspeaker bandwidth.

Advantageously, the directional horns are characterized by a wave guide cone defined by the side walls 31 so that the emission is symmetrical in the horizontal plane and asymmetrical in the vertical plane.

This geometric feature, in combination with the opposite position and the specific distance chosen between the acoustic centres of the horns A’, B’ allows to obtain a sound beam which in the range of frequencies of interest is focused in the preferential listening area S and has a reduced lateral dispersion with respect to the median vertical plane V1 ’ orthogonal to the emission cones of the horns A’, B’.

The present invention has been described according to preferred embodiments, but equivalent variants can be conceived without departing from the scope of protection granted.

Claims

1 . Directional acoustic speaker for broadcasting voice messages comprising a pair of mutually equal speakers (A, B; A’, B’), said mutually equal speakers (A, B; A’, B’), being configured to radiate within a passband preferably between 80Hz and 20kHz, driven by a common signal, arranged symmetrically and oriented in opposite directions with respect to a first vertical plane (V1) in order to emit a sound beam in said frequency range focused in a preferential listening area (S) adjacent to the speaker and with reduced lateral dispersion with respect to the median vertical plane (V1), arranged on a common horizontal plane (P) having a height (Q) with respect to a walking plane (G), wherein said mutually equal speakers (A, B; A’, B’) are fed with opposite polarity and are spaced apart by a mutual distance "d" substantially equal to half the wavelength of the lower limit of the loudspeaker bandwidth.

2. Speaker according to claim 1 wherein said pair of speakers comprises a pair of mutually equal loudspeaker lines (A, B) each formed by a plurality of aligned single loudspeakers (1 ).

3. Speaker according to one of the preceding claims, wherein said speaker lines (A, B) are oriented downwards with an angle (a) with respect to a horizontal plane preferably between 0° and 30°.

4. Speaker according to one of the preceding claims, wherein said loudspeaker lines (A, B) comprise eight aligned loudspeakers (1 ) of equal diameter for a total linear length of the line between 40cm and 100cm.

5. Speaker according to one of the preceding claims, comprising a screen (6) arranged above said loudspeaker lines (A, B).

6. Speaker according to claim 1 , wherein said pair of speakers comprises a pair of oppositely-oriented, controlled-directivity horn loudspeakers (A’, B’) provided with a wave guide cone (31 ) of geometry such that the emission is symmetrical in the horizontal plane and asymmetrical in the vertical plane.

7. Speaker according to one of the preceding claims, wherein said pair of mutually equal speakers (A, B; A', B') is arranged at a height (Q) preferably between 2.5 metres and 4 metres.

8. Speaker according to one of the preceding claims, wherein said pair of mutually equal speakers (A, B; A', B') is arranged at an adjustable height (Q) with respect to the walking plane (G).

9. Speaker according to one of the preceding claims, wherein said pair of mutually equal speakers (A, B; A', B') is supported at said height (H) by a pole (3).

10. Speaker according to one of the preceding claims, wherein said pair of mutually equal speakers (A, B; A', B') is supported at said height (Q) by vertical suspension means (4).

11 . Installation of a plurality of directional speakers according to at least one of the preceding claims arranged along said median vertical plane (V1 ).