[CEATEC 2019]
Invisible speakers revolutionize in-car design
The perfect speaker for near-future automotive interior design: an example of CASE
CASE, which stands for “Connected, Autonomous, Shared & Services, and Electric,” is the new trend sweeping the automobile industry. With it, the car interior is becoming the focus of greater attention. As automobiles come to serve the functions of communications terminals, and as the self-driving “connected car” eliminates the need for a human driver, the car interior will become a sort of “amenity room” where the passenger can sit back and relax. This will open up an opportunity for new services enabled by digital technology, such as large-screen audio-visual systems with superior sound quality, and the integration of communications systems with in-car equipment, including the seats and air-conditioning system. What makes all this possible is the emergence of quiet electric cars that do not make engine noise.
This near-future car interior is predicted to have a design where all the automobile controls are placed on the dashboard screen, to make the car spacious. In addition, further technological advancement is expected, which will allow you to control your car by speech; this will make it important to ensure that the car has good acoustic systems, including audio capability.
The car interior as an amenity room like never before
That is where PiezoListen™, TDK's newly developed piezoelectric speaker, comes in. A piezo speaker is a speaker that works based on the principle of vibration of the piezo element 1. A thin-film piezoelectric element called a piezo actuator is used to generate sound.
Being one of the thinnest speakers in the world (approximately 0.49 mm), PiezoListen may be installed anywhere, with no restrictions, to generate sound in any part of the car. This means that a speaker may be placed on the dashboard, or behind the screen, without the need to create a hole for it; this gives a far greater degree of freedom in interior design. In addition, PiezoListen works very well at the lower frequencies that have been considered a weakness for existing piezoelectric elements; it covers a wide range, from 400 Hz to 20,000 kHz.
The tremendous potential of PiezoListen, which turns everything into a speaker
PiezoListen comes in two types: an ultra-small and ultra-thin sound-positioning speaker that gives a great degree of freedom in designing sound position, and a wide-range speaker that produces sounds of higher pressure and greater range.
TDK's PiezoListen sound positioning speakers are already playing a prominent role in flat-screen TVs. In this application, several PiezoListen speakers are placed in the upper areas of the screen. In general, electromagnetic speakers 2 designed for flat-screen TVs are placed in the lower areas of the screen; when combined with PiezoListen speakers placed in the upper areas, they create a synergistic effect, raising the overall location of the sound field. This creates an acoustic system that gives users the feeling that they are experiencing the sound at a movie theater.
TVs with piezo speakers: an example
In addition to TVs and automobiles, PiezoListen speakers have an expansive range of possible applications, from tablets, laptops, wearables and smartphones, to VR headsets and touch panels on industrial devices. Furthermore, by creating piezoelectric vibrations in antiphase 3, the PiezoListen technology can potentially be applied to other areas than speakers. One such application is noise cancellation, which allows for the reduction of in-car noise and vibration noise of the automobile.
PiezoListen has been brought to life through TDK's proprietary multilayering technology and materials technology, which have led to the development of a low-profile, high-displacement piezoelectric element. Within this, the world’s thinnest piezoelectric element at approximately 0.49-mm thickness, over ten layers of piezoelectric sheets are stacked on one another, and are connected using a laser irradiation technology called “through-hole plating.” With its ability to turn everything into a speaker through piezoelectric technology, PiezoListen is set to offer entirely new solutions in a wide array of fields.
The PiezoListen™ Piezo Speakers
Terminology
- Piezoelectric (piezo) element: The phenomenon where voltages are generated in response to strains created by pressure applied to a material, such as crystals and certain ceramics, is called the piezoelectric effect. A piezoelectric (piezo) element refers to an electronic component that is used to harvest electricity by means of the piezoelectric effect, or, in reverse, to harvest vibration by applying a voltage.
- Electromagnetic speaker: A speaker that generates sound by using electromagnetic energy.
- Antiphase: Having a phase difference of 180°, so that one signal reaches its maximum as another reaches its minimum, and vice versa; because the two signals are in opposition, their combined value is zero.
