An array of speakers are fed from a single source of audio frequency sound but each speaker transmits the sound delayed by an amount which is determined by the distance between a particular speaker and a selected region in space, so that sound from each speaker constructively adds at the selected region in space. A sufficiently large number of speakers are employed so that when sound reaches a region in space at the same moment in time the audio volume will be increased substantially over sound in regions where there is not constructive interference. This simple technique allows audio frequency sound to be heard in only selected regions within the room or other auditory space. Multiple regions with multiple soundtracks can be created by simultaneously playing variously delayed soundtracks over each of the speakers in the array.

A hand-held mobile communication device, such as smart telephone, incorporating sensors and signal conditioning modules for measuring signals from external sources of electromagnetic radiation (EMR) in the low, radio, ultraviolet, and infrared spectral ranges. These include the detector for receiving and monitoring electromagnetic fields originating from various external sources of radiation that pose potential health hazards or may interfere with various electronic devices. The mobile phone equipped with such sensors could alternate between communication and monitoring functions. Other integrated EMR sensors are a photodiode for the ultraviolet detection to monitor the user’s sun exposure and a thermopile for non-contact measurement of temperature of humans or inanimate objects. This infrared sensor in combination with a photographic digital camera and a pattern recognition signal processing allows measuring temperatures at specific locations and from optimal distances to the surface of the object to enhance accuracy of non-contact temperature measurements.