Electronic devices, especially handheld devices, are getting smarter and smarter. For instance, the equipment or device is able to anticipate activities of the user thus instead of the user having to operate the device in order to adjust its settings to a new situation and/or position, “intelligent” functions, often featured by sensors, automatically adjust the settings of the device. For example, handheld devices are known having displays the content displayed on which rotates when the device is being rotated. Besides enabling features like this, sensing of the usage may especially essential for power saving mechanisms. Since battery lifecycle and standby time are critical properties among mobile devices, a standard procedure to automatically execute is switching off the display and keypad illumination of a mobile phone during a call, since a phone which is held next to a user's ear does not need a powered display. In view of that, it is essential to detect the actual situation of usage of the phone.
Known mobile phones generally comprise a keypad for making inputs to the phone, a display for visual feedback from the phone to the user, a processor for running the operation system and processing all the featured operations, storage means (e.g. RAM/ROM) for storing data of the operation system and other data, at least one loudspeaker (sometimes called receiver) for signalling of ringtones as well as for outputting of the other party's voice and at least one microphone for reception of the users voice, respectively, during a conversation, and at least one antenna for sending and receiving of electro-magnetic signals.
Recently, other features have become standard elements of mobile phones, such as photo and video camera, short-range-radio-data-exchange means, internet-browser, email client, hands-free-call capability etc., and thus, more and more different usage situations occur for the devices.
Four typical user scenarios for usage of a mobile phone are depicted in FIG. 1 denoted by a) to d). In situation a) the mobile phone is in front of the user's head, while the user is watching the display. In this situation the user can navigate through the mobile phone's menu, look for certain functions or browse through the internet, if featured. Another typical situation where the depicted position of the mobile phone is likely to occur is when due to an incoming call, the user is about to answer the call. In these situations neglecting single fingers of the user on the keypad, the front of the mobile phone is generally uncovered and since the user is interacting with the mobile phone, the illumination of the display is on.
In situation b) the mobile phone is at a user's ear, which is the normal position of a mobile phone during a call, i.e. hand-held use situation. In this use situation the front side of the mobile phone, in particular the portion or part containing the loudspeaker, is pressed against a user's ear. Since the user cannot look at the display anyway, the illumination of the display and the keypad may be turned off. In case the phone comprises a touch screen, the input function should also disabled in order to prevent the user's ear from inadvertently causing unwanted inputs to the phone. After terminating the call, the mobile phone may be positioned according to situation a), and the user will be watching the display of the mobile phone again in order to browse the menu, look up names or addresses, start another call or simply lock the keypad for example.
In situation c) the mobile phone is put on a horizontal surface, e.g. a table or desk, which is likely to occur, when the mobile phone is used for a hands-free call and the loudspeaker is driven at high volumes, i.e. a hands-free use situation. Users present during such call situations are able to look at the display of the mobile phone, browse through the menu and make inputs into the mobile phone, for example. In case of a video call, moving images of the dialogue partner, documents, or presentations might be displayed on the display of the mobile phone, which display is to be illuminated in this situation. Regardless occasional key pad inputs, the front of the mobile phone, especially the region where the loudspeaker is located, remains generally uncovered.
Situation d) shows the mobile phone in the user's pocket. This is the normal standby situation where no interaction from the user with the mobile phone is taking place, and thus the display illumination may be switched off.
Last but not least a not depicted situation, which is similar to situation d), is a mobile phone put on a table or elsewhere in the standby mode.
One sensor applicable to distinguish some of the mobile devices' actual positions is a proximity sensor, which measures some of the clues for the user scenario. The proximity sensor may detect an object, e.g. a human's head or ear, table-top etc., in front of the user interface of the phone. Additionally, a gravitational force sensor, i.e. accelerometer, can provide the horizontal or vertical position of the phone as a further clue. However, neither the proximity sensor nor the gravitational force sensor is capable to detect, whether the phone is held next to the ear during a call or in front of a face to watch the display.
Known concepts to cope with the challenge of detecting the usage situation of mobile devices are to provide light sensors and/or ultrasonic actuators/sensors in such devices. If the mobile device is held at a user's ear or head, the light sensor is exposed to less light and/or the distance to the user's cheek or head measured by the ultrasonic sensors falls below a certain threshold value, respectively and thus the display is switched off.
Smart features such as proximity estimation, however, are not limited to mobile devices. Voice control capability is expected to become more present in electronic devices in general in order to enable quick, easy and intuitive interaction with the user. This requires existence of at least one voice reception element such as a microphone in the electronic device to be voice-controlled.
U.S. Pat. No. 6,542,436 discloses a single speaker-single microphone detection arrangement for detecting if an object is in proximity to the device. Audio transducers already found in the device are used to realize the detection function, along with digital signal processing or equivalent means. For the proximity sensing a measurement signal is generated for driving an output acoustic transducer of the device. Then an input acoustic transducer of the device is monitored to detect the measurement signal; and determining that an object is in proximity to the device based on detected alteration of the measurement signal.
U.S. Pat. No. 5,619,476 discloses an electrostatic ultrasonic transducer formed on a semiconductor substrate by micro-machining.
U.S. Pat. No. 5,870,482 discloses a solid state condenser transducer.
Since electronic devices commonly are produced in mass production, hardware and production costs are to be reduced as far as possible. Thus, expensive additional actuator/sensor arrangements for estimating the proximity of a device and voice/sound input capability significantly lower the sales margins of such devices.
WO2008/111011 describes a MEMS microphone comprising a case with an open front side; a MEMS membrane mounted on one face of a base, the base being mounted inside the case on a substantially closed side; and a mesh covering the front side, substantially transparent acoustically to at least some of a range of operating frequencies at which the microphone is sensitive.
US2008/252595 describes an apparatus for virtual navigation and voice processing. The system may include, a computer readable storage medium having computer instructions for processing voice signals captured from a microphone array, detecting a location of an object in a touchless sensory field of the microphone array, and receiving information from a user interface in accordance with the location and voice signals.
JP2003/018696 describes providing an electret capacitor microphone which can also be used as an ultrasonic sensor by enlarging the characteristics up to a high frequency band while keeping the characteristics of low frequency band without increasing the size.