Method and apparatus to shape sound

Abstract

The invention relates to sonic steerable antennae and their use to achieve a variety of effects. The invention comprises a method and apparatus for taking an input signal, replicating it a number of times and modifying each of the replicas before routing them to respective output transducers such that a desired sound field is created. This sound field may comprise a directed beam, focus beam or a simulated origin. Further, “anti-sound” may be directed so as to create nulls (quiet spots) in an already existing sound field. The input signal replicas may also be modified in way which changes their amplitude or they may be filtered to provide the desired delaying. Reflective or resonant surfaces may be used to achieve a surround sound effect, a microphone may be located in front of an array of loudspeakers, beams of light may be used to identify the present focal position, a limiting device may be used to ensure that clipping or distortion is reduced when more than one input signal is output by the same device and the concept of beam directivity may be used to achieve input nulls or beams in a microphone made up of an array of input transducers. Further, sound field shaping information may be associated with an audio signal to be broadcast.

1 . A method of reproducing an audio signal, said method comprising:
 decoding an information signal associated with said audio signal:   processing said audio signal according to the information signal decoded in said decoding steps; and   reproducing said processed audio signal using an array of output transducers;   wherein said array of output transducers comprises at least four output transducers.   
     
     
         2 . A method according to  claim 1 , wherein said decoded information signal is a sound field shaping signal representing how the sound field should be shaped. 
     
     
         3 . A method according to  claim 2 , wherein said decoded information signal is a sound beam steering signal representing where the audio signal should be directed. 
     
     
         4 . A method according to  claim 2 , wherein said decoded information signal is a signal representing an origin from where the audio signal should appear to emanate. 
     
     
         5 . A method according to  claim 1 , wherein said processing comprises obtaining, in respect of each output transducer of said array of output transducers, a delayed replica of the audio signal delayed by a respective delay selected in accordance with the position in the array of the respective output transducer and in accordance with said information signal. 
     
     
         6 . A method according to  claim 1 , wherein said step of reproducing said processed audio signal comprises routing each of the delayed replica signals to a respective output transducer of said array of output transducers so that directed sound is achieved in accordance with said information signal. 
     
     
         7 . A method according to  claim 5 , wherein each of said respective delays are obtained from said information signal. 
     
     
         8 . A method according to  claim 5 , wherein each of said respective delays are calculated using an algorithm and said information signal comprises a 3D or 2D co-ordinate. 
     
     
         9 . A method according to  claim 5 , wherein each of said respective delays are calculated using a look-up table and said information signal comprises an address in said look-up table. 
     
     
         10 . A method according to  claim 9 , wherein said look-up table comprises a database relating a certain physical position with a set of delay values, said information signal comprises information indicating a certain physical position and said processing step comprises delaying said replica audio signals by amounts determined from the entry in the look-up table associated with the certain physical position indicated in the information signal. 
     
     
         11 . A method according to  claim 1 , wherein said information signal is multiplexed with said audio signal. 
     
     
         12 . A method according to  claim 11 , wherein said information signal and said audio signal are both digital signals and are time division multiplexed. 
     
     
         13 . A method comprising:
 deciding on how a sound field comprising an audio signal should be shaped during reproduction; and   coding an information signal according to the result of said decision;   wherein said information signal comprises information about how an array of at least four output transducers should output signals to reproduce said sound field.   
     
     
         14 . A method according to  claim 13 , wherein said coded information signal is a sound field shaping signal representing how the sound field should be shaped. 
     
     
         15 . A method according to  claim 14 , wherein said coded information signal is a sound beam steering signal representing where the audio signal should be directed. 
     
     
         16 . A method according to  claim 14 , wherein said coded information signal is a signal representing an origin from where the audio signal should appear to emanate 
     
     
         17 . A method according to  claim 13 , further comprising:
 associating said information signal with said audio signal.   
     
     
         18 . A method according to  claim 13 , wherein said coded information signal represents a focus position or simulated origin position and the step of coding said information signal comprises mapping the focus position or simulated origin position to a set of delay coefficients and coding the delay coefficients in said information signal. 
     
     
         19 . A method according to  claim 13 , wherein said coded information signal represents a focus position or simulated origin position and the step of coding said information signal comprises associating a location code with the focus position or simulated origin position and coding this location code into the information signal. 
     
     
         20 . A method according to  claim 18 , wherein said focus position or simulated origin position is determined relative to the array of output transducers to be used during reproduction of the audio signal. 
     
     
         21 . A device for reproducing an audio signal comprising:
 an input terminal for inputting an audio signal;   an input terminal for inputting an information signal;   means of decoding the information signal;   an array of output transducers comprising at least four output transducers;   a replicator and delaying means arranged to obtain, in respect of each output transducer of said array of output transducers, a delayed replica of the input signal delayed by a respective delay selected in accordance with the position in the array of the respective output transducer and in accordance with the decoded information signal;   means to route each of said delayed replica audio signals to a respective output transducer so that a sound field is achieved in accordance with said information signal.   
     
     
         22 . A device according to  claim 21 , further comprising a de-multiplexer connected to said audio signal input and said information signal input so that a signal obtained by multiplexing an audio signal and an information signal may be input into the device. 
     
     
         23 . A device according  claim 21 , wherein said array of output transducers comprises a regular pattern of output transducers in a two-dimensional plane. 
     
     
         24 . A device according to  claim 23 , wherein each of said output transducers has a principal direction of output perpendicular to said two-dimensional plane.