Active noise control system with horn sound feature

An active noise control system for use onboard a vehicle normally provides noise cancellation of engine sounds. The speaker of the active noise control system also emits a horn sound responsive to appropriate commands from a controller that receives a horn switch signal from a horn switch supported on a steering wheel assembly. The active noise control system controller enters a power saving mode when the vehicle ignition is turned off and the vehicle is not running. A horn switch activation during the power saving mode wakes up the controller so that the controller unmutes an amplifier and drives the speaker to emit the desired horn sound.

BACKGROUND OF THE INVENTION

This invention generally relates to active noise control systems for vehicles. More particularly, this invention relates to operating an active noise control system to provide a horn sound when a vehicle is not running.

Most vehicles include a horn that is activated by pressing or more switches typically mounted on a steering wheel assembly. The horn is properly used to notify other drivers or pedestrians of a vehicle's presence or approach, for example. Typical horn assemblies include a physical horn component mounted within the engine compartment that emits the horn sound responsive to appropriate switch activation.

Active noise control systems are well known. On modern vehicles, active noise control systems operate to cancel out noises associated with air intake assemblies, for example. A noise control system typically includes a speaker that is driven to emit a sound that cancels out engine noise sounds that otherwise may be noticed by an individual within the passenger compartment. A controller drives the speaker to provide the necessary noise cancellation signal or sound to provide the desired effect.

With the advances available in electronics onboard vehicles, those skilled in the art are always striving to provide additional features and functions for the consumer. Further, there is always a need to strive for minimizing the expenses associated with supplying vehicle components to manufacturers. This invention takes advantage of the capabilities of an active noise control system and provides further capabilities that eliminates otherwise needed separate components such as a horn.

SUMMARY OF THE INVENTION

In general terms, this invention is an active noise control system that also provides a horn sound function even when the vehicle is not running.

One example system designed according to this invention includes a speaker. A controller drives the speaker to produce a desired sound. The controller operates in a normal mode while the vehicle is running and typically drives the speaker to produce a noise cancellation sound to cancel out noises associated with operation of the engine so that such noises are not noticeable within the vehicle passenger compartment. The controller also operates in a power saving mode when the vehicle is not running. The controller wakes up from the power saving mode responsive to a horn switch activation that occurs when the vehicle is not running. The controller then drives the speaker to emit a horn sound and returns to the power saving mode after the horn switch activation is complete.

In one example, the system includes an amplifier associated with the speaker. The controller mutes the amplifier in the power saving mode and unmutes the amplifier responsive to the horn switch activation so that the desired horn sound is produced.

The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of a currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1schematically shows a vehicle20that includes an active noise control system22. A speaker24and an amplifier26are driven by a controller28. The speaker24is associated with, for example, the air intake manifold of the vehicle to cancel out noises associated with engine operation that would otherwise be noticeable within the vehicle passenger compartment. Known active noise cancellation techniques provide such results.

A steering wheel assembly30is supported within the vehicle passenger compartment. A horn switch32, which operates in a conventional manner, is supported on the steering wheel assembly30. In the example arrangement, the horn switch32does not activate a separate horn device supported within the engine compartment. Instead, the noise control system22provides the horn sound using the speaker24. The controller28responds to activation of the horn switch32by driving the amplifier26and speaker24to emit a preselected horn sound.

The controller28operates in a normal operation mode while the vehicle is running. The controller28normally provides active noise control in a conventional manner. In the event that the horn switch32is activated, the controller28detects a horn switch activation and interrupts the active noise control temporarily so that the speaker24can be used to provide the desired horn sound.

It is desirable to provide an individual the ability to activate the horn even when the vehicle is not running. The controller28enters a power saving, standby mode when the ignition is turned off and the vehicle is not running. The controller28interprets a horn switch activation as a wake up signal when the controller is in the power saving mode. The controller28then responds to the horn switch activation by appropriately driving the speaker24to emit the horn sound.

FIG. 2illustrates an example control strategy in flow chart form. At42the controller28is in the power saving mode. A horn switch activation at44provides a wake up signal to the controller28. In one example, the horn switch activation produces a low digital signal (i.e., 0) that is interpreted by the controller28as a wake up signal. Once awakened, the controller28continues checking for a horn switch activation signal every ten milliseconds at46. The controller28unmutes the amplifier26at48and drives the speaker24to emit the desired horn sound at50. In the illustrated example, the horn sound is generated for 200 milliseconds. The controller28continues checking for horn switch activation and driving the speaker24to emit the horn sound as long as the signal is present.

Once the horn switch32is released, the determination at46is negative. The controller28then mutes the amplifier at52and returns to the power saving mode at42.

In one example, the controller28comprises a digital signal processor (DSP). The DSP wakes up responsive to the horn switch activation signal and then controls the amplifier26and speaker24as necessary to achieve the desired horn sound. In another example, the controller28includes a microprocessor portion and a DSP portion. In this example, the microprocessor portion is responsible for handling the horn activation when the controller is in the power saving mode. In this latter example, the DSP remains in shutdown mode during horn activation when the vehicle is not running.

Those skilled in the art who have the benefit of this description will realize how best to select and arrange the electronics to achieve the horn activation strategy that best suits their particular needs.