Besides hearing, the perception of sound is also based on the sense of touch. Sense of touch is mostly a subconscious sense working in the background, giving essential information on the condition of the body (e.g. pain sensation) and directing motoric action (skin sense tells you when you have a good grip of the object you're holding). When listening, the attention is directed to the sound coming to the ears through air, or airborne sound. However, almost always sound also causes some mechanical vibration in the proximity of the listener, for example in the seat, clothes or directly on skin. This sound, structure-borne sound that is felt as tactile sensation, makes the listening experience more intimate and deeper. The vibration is especially felt with low frequency sounds. Also sounds somewhat higher than in the bass frequencies are perceivable. The sense of touch of the skin is typically most sensitive in the frequency range of 50-300 Hertz, and in some parts of skin vibration is perceivable up to almost 1000 Hz. Through the sense of touch—haptically—also the hearing-impaired can perceive sound information, for example speech.
For the existing sound reproduction systems with current technology, it's typical that listening is possible either from a distance (loudspeakers) or close to the device (headset). Current prior art technology does not offer loudspeakers for listening both from a distance and through ear contact.
There exist small loudspeakers that are used for close up listening, for example those used in a pillow. There are, however, limitations to this kind of prior art solutions that are based on airborne sound radiation; a) the sound is sharpest right next to the loudspeaker elements, b) the sound is spatially localized to loudspeaker element locations, and c) there is no proper bass reproduction.
It is well-known that powerful low frequency loudspeakers (subwoofers) or specific mechanical vibrators in, for example, the seat or the headset, can be used to add tactile sensation to the listening experience.
Thus, with prior art solutions, the skin sensation complementing the listening experience is typically produced by solutions that are separate from the listening device itself.
The following four publications represent prior art technology. The Japanese publication JP2004057261 presents a pillow with a loudspeaker in it. Besides the loudspeaker, the pillow also contains padding. The loudspeaker includes parts that touch the user's neck when they rest their head on the pillow. In the United States patent application US20130228392, the loudspeaker is surrounded by a waterproof layer of polymeric foam. Besides being waterproof, the layer enhances sound producing vibrations. In the US patent application US20120039057, the padding is meant to electrically insulate a piezoelectric board. A German publication DE102011015747 presents a plate meant for a wall-mount loudspeaker. The board contains foam of a ceramic material, and the board is partly lined.