Bone conductive speakers, which allow sound to be heard merely through contact with any part of the head, are used in more and more applications.
When we hear sound, sound waves enter the ear and strike the eardrum, which converts the air vibration into physical vibration, and conveys that vibration to the snail shell-shaped auditory organs. These vibrations are converted into signals, carried by nerve cells to the brain.
However, we also recognize as sound vibrations that reach the auditory organs without passing through the eardrum, such as those passing through the bones of the head. We call this type of hearing "bone conduction." |
Our piezoelectric bone conductive speakers are covered with an organic material, a design unique to NEC TOKIN. From the outside, they look like simple thin plates, hardly capable of producing sound. However, hearing is believing, and they not only produce sound, but offer the advantages of compact size, light weight, minimal sound leakage, and low energy consumption.
Using a simulator to propagate audible signals to the inner ear, frequency characteristics can be adjusted to best suit the user, and provide natural sounding audio. |
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EXAMPLE OF USE 1: EARPHONES
The area around the entrance to the ears and especially the antilobium (slight bulge at the front of the entrance to the ears) are sensitive to sound vibrations, and recognize these sound vibrations as sound when sound vibrates these areas or near these areas.
A small, lightweight stylus piezoelectric vibrator with an integrated ring placed to the entrance of the ears is the source of sound vibration. Sound vibrations created by the piezoelectric vibrator strike extremely effectively around the ears, with some of the sound recognized through the eardrum, and other sound recognized from the cartilage to the auditory nerves at the back of the ears. The rings placed to the ears to retain the vibrators do not block the ears, so they don’t block out ambient sound like traditional earphones do.
These earphones are lightweight because they use small, high output piezoelectric vibrators possessing layering technology. (Less than 3 g)
Very little sound bleeds from these earphones so they don’t disturb the surroundings. Materials and designs of the rings placed to the ears can be selected that are pain-free on the ears.
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EXAMPLE OF USE 2: HEADSET
This headset is lightweight (less than 30 g), has virtually no sound leakage and applies very little pressure to the face.
It’s perfect as a sound device for appreciating music and listening to information in both ears.
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EXAMPLE OF USE 3: CAP WITH SPEAKERS
This is an example of air conduction speakers with piezoelectric bone conduction speakers mounted to a cap with earmuffs.
The cap's earmuffs are open sound emitters without the pressure felt by wearing headphones, making them high volume speakers for the user. They also only leak a tiny amount of sound to the surroundings.
Our company’s piezoelectric bone conduction speakers are thin & lightweight not cumbersome when the earmuffs are worn. The earmuffs can be stored on the inside of the cap when not in use. This can be used in a wide variety of ways for appreciating music during outdoor activities, listening to the radio during a sporting event or for wireless business communications.
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When Speakers are in Use
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When Earmuffs (Speakers) Are Stored
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| Bone Conduction Speaker Component: Product Summary |
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ITEMS |
KDS-UM-01 |
KDS-UM-05 |
REMARKS |
| 1 |
Appearance |
See photo |
See photo |
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| 2 |
Size |
33 x 18 x 3 |
34 x 5 x 4.5 |
Without terminals |
| 3 |
Weight |
3.6g |
2.1g |
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| 4 |
Terminal-to-Terminal Electrostatic Capacity |
1.2μF±15% |
800nF±15% |
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| 5 |
Maximum Operating Voltage |
7.5 Vrms |
7.5 Vrms |
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| 6 |
Sound Output |
See figure below |
See figure below |
Reference value |
KDS-UM-01
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KDS-UM-05
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