Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Driven diverse static structure
Reexamination Certificate
2000-02-10
2002-04-23
Tran, Sinh (Department: 2743)
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Driven diverse static structure
C381S423000, C381S426000
Reexamination Certificate
active
06377695
ABSTRACT:
DESCRIPTION
1. Technical Field
The invention relates to trim panels, e.g. for the passenger cabin of a vehicle such as an automobile and more particularly to trim panels incorporating loudspeakers.
2. Background Art
A number of approaches have been tried for achieving good quality sound reproduction in vehicles such as automobiles. Conventional pistonic loudspeakers of good quality, efficiency and satisfactory loudness use large magnets driving cone diaphragms resulting in an assembly including the loudspeaker chassis or basket of appreciable depth typically 6 to 10 cm.
Space is limited in a vehicle interior with little scope for sealed or tuned box volumes typically used for cone-type pistonic speakers. Often speakers have to be installed in non optimal positions well away from the head locations of the occupants, for example, on the rear parcel shelf, on the lower door panels out of the way of the window winder mechanism, or at the extremities of the dashboard, to supplement the sound from the poorly located door speakers. Six speaker arrangements are typical in an attempt to address the problems caused by poor location driven by the need to find significant panel depth to locate conventional speaker drivers.
Rear parcel shelf speakers are located behind the passengers, far from the front seats and are impaired by proximity to the cavity formed by the rear window glass and the parcel shelf. Potentially each such speaker is also located too near the nearest passenger resulting in a local excess of loudness.
Door-mounted speakers are placed in the noisiest part of the vehicle and suffer from vibration, door panel resonance, road noise transmission and engine noise. They are almost inaudible for rear seat passengers and are placed well off axis for front seat occupants. In addition their acoustic output may be severely obstructed by an occupant's leg(s).
A further pair of loudspeakers which may be located on the dashboard often suffer from poor mounting technique impairing the frequency response and endure local reflections from the windscreen glass. They are inadequately placed to give satisfactory spread of the two stereo channels. Each is usually too near to the nearest occupant.
In our U.S. patent application No. Ser. No. 08/707,012 filed Sep. 3, 1996 these problems are addressed with the object of giving greater aural comfort, reduced installation cost, greater signal to noise ratio, greater efficiency, more uniform stereo and multi channel sound for all the vehicle occupants, reduced weight, simplified vehicle wiring and potentially higher quality sound.
Distributed mode bending wave resonant panel loudspeakers as described in our application Ser. No. 08/707,012 use a diaphragm which is usually flat and is relatively slim, driven by a low excursion low profile electromechanical transducer, typically electrodynamic although other types are suitable including piezo, if the acoustic characteristics of the radiating panel are satisfactorily matched to the type of transducer and to the available amplification.
DISCLOSURE OF INVENTION
From one aspect the present invention is a vehicle having a passenger compartment, a trim panel, e.g. a roof lining, forming a lining in the passenger compartment and a loudspeaker in the passenger compartment, characterised in that the loudspeaker is in the trim panel and comprises an integral resonate acoustic radiator and a vibration exciter mounted on the radiator to launch bending waves into the radiator to cause it to resonant to produce an acoustic output, and a radiator periphery integral with the radiator and the surrounding trim panel. The integral periphery may be moulded integrally with the trim panel or may be permanently fixed to the trim panel to make it integral therewith. Equally, the acoustic radiator may be moulded integrally with the trim panel or may be permanently fixed thereto to make it integral therewith. Possibly the periphery could be moulded integrally with the trim panel and the acoustic radiator could be permanently fixed to the trim panel, e.g. by adhesive means, to make it integral therewith.
The radiator may be of the same material as the trim panel or may comprise a stiff lightweight panel. The integral periphery may define a clamped edge termination for the radiator. The clamped edge termination may be formed by an integrally moulded stiffening rib surrounding the radiator.
The radiator may be stiffened by one or more ribs extending over its surface.
The vibration exciter may be inertial. The vibration exciter may be electrodynamic.
From another aspect the invention is a trim panel, e.g. a roof lining for a vehicle passenger compartment, characterised in that the trim panel comprises an integral acoustic radiator and a vibration exciter mounted on the radiator to launch bending waves into the radiator to cause it to resonate to produce an acoustic output, radiator periphery integral with the radiator and the surrounding trim panel.
The radiator may comprise a stiff lightweight panel.
The integral radiator periphery may define a clamped edge termination for the radiator. The clamped edge termination may be formed by an integrally moulded stiffening rib surround the radiator.
The radiator may be stiffened by at least one rib extending over its surface.
The vibration exciter may be inertial. The vibration exciter may be electrodynamic.
The trim panel may comprise a plurality of resonant radiators. Where the trim panel is a vehicle roof lining for a passenger compartment, a resonant radiator may be positioned adjacent to each passenger position in the compartment.
It is fundamental to the present invention that the designated sound radiating area is of the distributed mode type in the required frequency range. In contrast to other kinds of radiator, e.g. near pistonic and local area excited types which have essentially point source coherent radiation characteristics, the distributed mode type is excited over a significant area and has a diffuse non-directional output even at extreme off axis angles, without significant variation with frequency. This provides a good radiation pattern for the confined spaces within a vehicle passenger cabin.
The panel may be adapted to operate at least partly below coincidence frequency, and may be adapted to operate mainly or wholly below coincidence frequency.
The entire periphery of the acoustic member may be clamped or alternatively one or more edges of the member, e.g. a rectangular panel, may be clamped. Full clamping enables the design of the loudspeaker assembly to be predictable in mechanical terms, and also facilitates the creation of a loudspeaker assembly which is relatively robust in construction, compared to a resonant panel loudspeaker in which the panel edges are free or are resiliently suspended.
The clamping of the peripheral portion(s) or edge(s) of the acoustic member may be achieved in any desired manner e.g. by rigidly fixing the edge(s) to a frame or the like by means of an adhesive or by mechanical means e.g. involving clamping the edge(s) between frame members. The edge clamping may also be achieved by moulding techniques such as injection moulding of plastics materials by forming the edges of the member with integral thickened surround portions of sufficient rigidity to terminate edge movement of the acoustic member. Co-moulding of the acoustic member and the thickened edge may be appropriate. Such moulding techniques may be particularly suitable where the acoustic member is formed as a monolith and may be readily achievable in economic manner.
It will thus be appreciated that the term ‘clamped edge’ is intended to encompass all forms of edge restraint.
Clamping may also be used to define one acoustic member within another larger acoustic member. Thus a large acoustic panel Intended for mid/low frequency operation may be moulded to include a smaller high frequency acoustic panel defined by a clamped perimeter formed by stiffening ribs.
The clamping action can be designed to have a desired mechanical termination impedance to control the reverberation time
Azima Henry
Colloms Martin
Ellis Christien
Foley & Lardner
New Transducers Limited
Tran Sinh
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