Audio systems are included in virtually every automobile manufactured today. These audio systems are typically designed for use while the doors, tailgates, and other openings to the passenger compartment are closed. However, people often choose to listen to their automobile audio system while they are outside of their vehicle, such as while they are camping or “tailgating” at a sporting event. Because traditional automobile audio systems are not designed for this type of use, listeners may not enjoy as high a quality sound presentation as they could if the system were designed for outdoor use.
The acoustic characteristics of a typical vehicle with all of its doors closed will generally be significantly different than the acoustic characteristics of the same vehicle with its tailgate (or one of its doors) open. For example, the linear transfer function from each speaker element to various listening locations will be markedly different in each circumstance. Furthermore, opening or closing of the tailgate significantly alters the acoustic characteristics of the cabin space.
Accordingly, it is desirable to have an automobile audio system which is able to operate in two modes: one mode where one or more parameters of the audio system are configured to better optimize sound quality while the doors (to include tailgates) are closed and a second mode where one or more parameters of the audio system are configured to better optimize sound quality while one or more of the doors, such as a tailgate, are open.
Additionally, users may wish to operate their automobile audio system while the engine is not running and thus drain power from the automobile's battery. It is therefore desirable for an automobile audio system to monitor one or more operating conditions of the battery and adjust system performance in order to extend the maximum period of time the audio system can operate from battery power. It is also desirable to monitor one or more operating conditions of the battery to ensure operation of the audio system does not result in a condition where sufficient battery charge (to allow the automobile to be restarted) is no longer available.
It should be noted that the terms automobile and vehicle are used synonymously in this description and refer to any self-propelled passenger vehicle used for land transport, including cars, trucks, pick-up trucks, sport utility vehicles, and the like. Additionally, the term tailgate refers to a hinged door of an automobile which provides access to a rear opening of the automobile. A tailgate may be hingedly connected to the top, bottom, or side of the frame of the automobile.