What are the inherent advantages of USound MEMS speakers?
If comparing the USound MEMS speakers to conventional and Balanced Armature speakers a few inherent advantages present themselves:
- Smaller size; especially the flatness of USound MEMS speakers is unbeatable
- Practically no heat generation (especially compared to the electrodynamic speakers)
- Much lower mass; overall less mass and lower moving mass -> lower vibrations
- No electromagnetic radiation
- To describe these advantages in more detail, check the following sub-chapters.
Smaller size; thinness of the speaker
With conventional speaker speakers (electro dynamic and Balanced Armature likewise) the performance strongly correlates with their size. Simply put: bigger speaker equals more SPL. This is especially true if high excursions are needed (in free field and with low frequencies).
With USound MEMS speakers this relationship between size and SPL is not that prominent. Which poses a disadvantage but also an advantage. The more space is available the worse the MEMS speaker becomes in comparison with any conventional speaker. On the other hand, if size (especially flatness) is crucial, USound MEMS speaker will not suffer as significantly as any conventional speaker.
For example, in terms of thickness USound MEMS speakers allow a range below 1.5mm (1mm is currently under development). Within any electro dynamic speaker such a thickness would extremely reduce the magnet size rendering the electro-mechanical transmission almost noneffective, resulting in a very little SPL output.
No heat generation
As it is known only resistive electric losses produce heat. While in conventional speakers the ohmic resistance is unavoidable and needed, USound MEMS speaker do not have such an element. This results in a much smaller transformation of electric into thermal energy.
In conventional speakers a coil is used for the energy transformation from electric to mechanic. Unavoidably the wire inside the coil poses a resistive electric resistance. This is partially needed to keep the current flow nearly constant and subsequently produce a constant force, but also produces a significant transformation of electric energy into thermal energy resulting in a strong hearing of the coil. In typical mobile phone speakers coil temperatures reach up to more than 70°C (in typical 23° room temperature surrounding).
USound MEMS Speakers are working with a capacitive element to transfer electric energy into mechanical energy. The impedance is therefore almost only reactive, resulting in nearly no conversion into thermal energy.
Smaller (moving) mass; lower vibrations
In comparison to conventional speakers USound MEMS speakers use much less heavy materials. Electro dynamic speakers and BAs need at least magnets which will consist of a metal. Additionally, BAs usually have an aluminum housing to keep the size small (due to thin walls) and to get some kind of electromagnetic radiation protection.
Furthermore, the moving part of any conventional speaker either consists of a coil (in case of electro dynamic speakers) or a magnetic anchor (in case of BAs) which both have a high mass compared to silicon, which is used in USound MEMS speakers to make the membrane move.
The lower moving mass means inherently a lower vibration force on the surrounding. Following the Newton law ; the moving mass directly influences the force which will be produced and has to be absorbed by the surrounding housing and fixation.
No electromagnetic radiation
Conventional speakers rely on the electro dynamic principle also known as “Lorentz force”, which uses a magnetic field to produce a mechanical force. This entails quite some variating magnetic field which will radiate into the surround. Especially sensible sensors can easily be disturbed by this unwanted electromagnetic pollution.
On the other hand, USound MEMS speakers use the piezo electric principal, which produces no electromagnetic radiation. This cancels the need for any magnetic shielding in mobile devices between speaker and other sensitive parts (like sensors).