System of sound transducers with controllable directional properties

• US 7,343,018 B2
• Filed: 09/12/2001
• Issued: 03/11/2008
• Est. Priority Date: 09/13/2000
• Status: Expired due to Fees

• Current Assignee: PCI Limited (Chuan HUP Holdings Limited)
• Original Assignee: PCI Limited (Chuan HUP Holdings Limited)
• Inventors: van der Werff, Johan
• Primary Examiner(s): Mei; Xu
• Application Number:
  US10/363,839
• Publication Number:
  US 20040028238A1
• Time in Patent Office: 2,372 Days
• Field of Search: 381/80, 381/82, 381/85, 381/300, 381/332, 381/335, 381/89, 381/116, 381/182, 381/186, 381/387, 181/144
• US Class Current: 381/80
• CPC Class Codes: H04R 1/403 loud-speakers
• CPC Class Codes: H04R 3/12 for distributing signals to two or more loudspeakers specially adapted for hearing aids H04R25/407

Abstract

The invention relates to loudspeaker systems or loudspeaker columns as used in public address systems and at (pop) concerts. Such systems heretofore possess a frequency-dependent coverage angle and strong second and third order side lobes. The invention describes formulae of the voltage to be applied to the separate loudspeakers of the loudspeaker column, which makes it possible to realize the constant coverage angle over the entire frequency range and to suppress the side lobes to a far-reaching extent.

Claims

1. A system of sound transducers, in particular loudspeakers, comprising n loudspeakers (n=2 . . . x) which are arranged according to a regular pattern substantially along one line in a column-shaped housing, wherein the sound transducers are each provided with an associated filter, which filters all receive an audio signal at an input thereof and deliver a signal at an output thereof to the associated sound transducer, in order that the sound transducers in operation possess a signal pattern with a predetermined characteristic, characterized in that means are provided for applying to each loudspeaker n in the column a voltage V_n, according to:

$V_n=V·<br><br>{\mathrm{e<br><br>}}^{-0,5<br><br>{\left(\frac{\mathrm{\alpha <br><br>}·<br><br>{\mathrm{dls}}_n}{<br><br>{\mathrm{dls}}_{\max }<br><br>}\right)}^2}$

wherein;

V_n;

the voltage on the terminals of loudspeaker n;

V;

the voltage on the terminals of the loudspeakers in the acoustic center of the column;

dls_n;

the distance in meters of loudspeaker n to the acoustic center of the column;

dls_max;

the distance in meters to the acoustic center of the loudspeaker farthest removed therefrom;

α

;

parameter depending on coverage angle, frequency and array dimension according to the relation;

$\mathrm{\alpha <br><br>}=\mathrm{\beta <br><br>}·<br><br>f·<br><br>\frac{l_{\mathrm{array}}}{k}$

wherein;

β

;

the vertical coverage angle in degrees, which is fixedly chosen for a particular design;

f;

the frequency in Hz;

l_array;

the length of the array in meters;

k;

constant=14.10³ given the units mentioned for β

, f and l_array.

2. A system of sound transducers, in particular loudspeakers, comprising n loudspeakers (n=2 . . . x) which are arranged according to a regular pattern substantially along one line in a column-shaped housing, wherein the sound transducers are each provided with an associated filter, which filters all receive an audio signal at an input thereof and deliver a signal at an output thereof to the associated sound transducer, in order that the sound transducers in operation possess a signal pattern with a predetermined characteristic, characterized in that means are provided for applying to each loudspeaker n in the column a voltage V_n, according to:

V=a−

b·

cos(m)+c·

cos(2.m) 

 

(2)

wherein;

a, b and c are the constants which determine the window,

m;

is m^th fraction of unit circle (in radials) according to;

$m=\frac{0,1,2<br><br><br><br>\mathrm{\dots <br><br>}<br><br><br><br>\left(n-1\right)}{\left(n<br><br><br><br>l<br><br><br><br>s-1\right)}·<br><br>2<br><br><br><br>\mathrm{\pi <br><br>}$

wherein;

nls;

operative number of loudspeakers in the array, depending on coverage angle and frequency according to the relation below;

$\mathrm{nls}=\frac{k}{\mathrm{\phi <br><br>}·<br><br>f·<br><br>c·<br><br>d}$

wherein;

φ

;

desired coverage angle in degrees

f;

frequency in Hz

c;

sound velocity (ca. 340 m/sec in air)

d;

center-to-center distance between the transducers in meters

k;

constant to some extent-depending on window type.

3. A system according to claim 2, wherein a=0.5, b=0.5 and c=0.

4. A system according to claim 2, wherein a=0.54, b=0.46 and c=0.

5. A system according to claim 2, wherein a=0.42, b=0.5 and c=0.08.

6. A system of sound transducers, in particular loudspeakers, comprising n loudspeakers (n=2 . . . x) which are arranged according to a regular pattern substantially along one line in a column-shaped housing, wherein the sound transducers are each provided with an associated filter, which filters all receive an audio signal at an input thereof and deliver a signal at an output thereof to the associated sound transducer, in order that the sound transducers in operation possess a signal pattern with a predetermined characteristic, characterized in that means are provided for delaying in time the signal that is applied to a loudspeaker n in the column, according to the formula

$t_n=\max$

⁢

t ·

ⅇ

- 0.5 ⁢

( α

·

dls n 

dls max 

) 2

wherein;

t_n;

the delay time of transducer n

maxt;

the maximum time difference between the transducers (depending on frequency, extent of broadening)

dls_n;

the distance of loudspeaker n to the acoustic center;

dls_max;

the distance of the loudspeaker farthest removed from the acoustic center;

α

;

parameter which fits the effect sought, normally ca. 3.

7. A system according to claim 6, wherein α

=33.

8. A system of sound transducers, in particular loudspeakers, comprising n loudspeakers (n=2 . . . x) which are arranged according to a regular pattern substantially along one line in a column-shaped housing, wherein the sound transducers are each provided with an associated filter, which filters all receive an audio signal at an input thereof and deliver a signal at an output thereof to the associated sound transducer, in order that the sound transducers in operation possess a signal pattern with a predetermined characteristic, characterized in that means are provided for applying to each loudspeaker n in the column a power P_f according to:

$P_{f,\mathrm{\phi <br><br>}}=P_{f,0}·<br><br>{\mathrm{e<br><br>}}^{-0,5<br><br>{\left(\frac{\mathrm{\alpha <br><br>}·<br><br>\mathrm{\phi <br><br>}}{2<br><br><br><br>\mathrm{\pi <br><br>}}\right)}^2}$

wherein;

P;

the sound pressure in Pascal (at frequency and angle with main axis)

φ

;

the angle (in radials between −

π and

π

) with respect to the main axis of the transducer, in the direction of the array (0 is the main axis)

f;

the frequency at which the directional effect is determined

α

;

parameter depending on frequency and transducer dimension according to the relation below;

$\mathrm{\alpha <br><br>}=\frac{f·<br><br>d}{k}$

wherein;

d;

the center-to-center distance between the transducers

k;

a constant.

9. A system according to claim 8, characterized in that the value of k is between 18 and 25.

10. A system according to claim 9, characterized in that k=18.