The pick-up efficiency of a microphone may vary depending on the direction from which the sound comes. This characteristic can be an unavoidable consequence of the design of the microphone or a conscious design to obtain properties for specific purposes. Some microphones also have variable characteristics. This is usually illustrated graphically in diagrams showing the characteristics. In this case the microphone is located in the centre with its front directed upwards in the diagram.
Neodymium magnets, or rather NdFeB, are products produced by powder metallurgy and based on neodymium, iron and boron, which makes magnets that are impressive in relation to their strong magnetic field. They are actually the strongest permanent magnets that can be produced today.
What is not as well known is that neodymium magnets are susceptible to corrosion in their raw state. When the magnets are exposed to humidity they can corrode, which can destroy the magnet if the magnets are not treated correctly from the outset. The magnets can be surface treated to prevent corrosion.
Many applications for electric motors involve the conversion of a rotary motion to a linear motion, e.g. in actuators, XY tables, zoom or focus in optical applications etc.
This can be done in many different ways, with different advantages and disadvantages, which are suitable for different applications. In this article we look at some of the common methods of producing linear motion with electric motors.