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May 9, 2019
The THD peak at ~10 kHz stems mainly from a mode of the MEMS at 21 kHz. When the MEMS is excited with 21kHz it resonates strongly and produces movement and subsequently a higher SPL. Due to small inherent non-linearities in the movement of the MEMS, 10.5 kHz will produce a small frequency component at…
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April 30, 2019
USound specifies and measures Ganymede MEMS speakers, Achelous and Adap, in both acoustic domains: in the Baffle and in the Coupler (artificial ear). For both setups, proprietary measurement adapters are used to fit the standardised setup. In Baffle In the case of the baffle, the measurement adapter places the MEMS speaker with appropriate sealing inside…
Learn moreApril 11, 2019
The baffle measurement is standardised in the IEC 60268-5 [1], even though in everyday applications, no baffle is present. So why does the industry rely on this particular setup? There is one main reason: it is universal. The baffle is basically just a massive wall which separates back and front side of the speaker. The…
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April 4, 2019
USound’s technology is based on piezoelectricity. Crystals with these properties are for example aluminium nitride (AlN) or lead zirconate titanate (PZT). These materials expand or shrink in an electric field. In a practical configuration, such an electric field is generated between electrodes, covering a piezoelectric layer. This stack is put on top of a substrate…
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April 3, 2019
The current versions of Ganymede MEMS speakers have two land pads on the backside. They are shaped differently to mark the polarity. There are different ways on how to bring electricity to these contacts: Hand soldering on the pads: It is worth noting, that the speaker is not able to withstand the normal reflow process…
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April 3, 2019
Sealing the front from back side of the speaker is critical to obtain the best acoustic output. This can be achieved by two methods: Glueing the speaker into the application’s housing. In this case, the glue can be applied around the speaker or on the cover. Care must be taken to: Obtain a fully sealed…
Learn moreJune 5, 2018
As everyone knows the further away a sound source is, the quieter the sound will be. This is due to the surface expansion of the affected space. One can imagine an ideal point source producing a sound field that moves like an expanding sphere into all 3 dimensions. This means that for doubling the distance…
Learn moreJune 4, 2018
The baffle measurement represents a special case of free field measurement. However, in this case, the sound is propagating through the air as a wave. In case of miniature speakers, the transition between mechanical movement and air pressure is poor, that’s why very high excursions are needed to produce high SPL (e.g. very rough example:…
Learn moreJune 4, 2018
Acoustics is based on vibrating air pressure. The higher the amplitude of the vibration the higher the SPL. To create these pressure changes a moving membrane is used in loudspeakers. Paying a closer look at the situation, one can see, that when the membrane moves forward, an over-pressure created in front of the membrane. On…
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June 4, 2018
First, we should clarify how power consumption is typically measured with electro-dynamic speakers or BAs. Since the impedance of these speakers is roughly constant over frequency (typically 4, 8 or 32Ω), this impedance value is taken as “nominal”. With this, a very simple transformation from a result obtained with a constant voltage into a result with…
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