Microphones

17.02.2020 0 Matt Jackson
Microphones

How did people get clear, loud sound to travel before the invention of the electric microphone in the 19th century? Shouting, screaming, yelling would not allow sound to travel across a large crowd or to other times and places. Really, up until the electric microphone was invented there was no good way to amplify sounds enough so that you could hear it across large crowds or in other locations. After someone figured out how to convert sound energy into electricity the electric microphone was born and with that, we actually garnered the remarkable ability to send the sounds we hear now, including music, voices and random noises to other places and times. For example, we could record a song or a speech in present day in Canada and hear it again in thirty years over in the UK. So, how does this truly amazing technology work? 

Microphones are used by converting incoming sound into outgoing electricity. Saramonic mics can be used by professionals that are broadcasting a podcast, musical recording or audio which must be of higher than average quality. If you look at one closely you will see a metal grille on the wind screen (the part of the microphone that you speak into). That metal grille actually has a purpose beyond looking cool. It is the part of the microphone that reduces any wind noises or pop sounds. 

The opposite of a microphone is technically a loudspeaker. Loudspeakers take the incoming electrical energy and change it into the sounds you can hear.  

This article is brought to you by Saramonic UK - the one stop shop for microphones.

Microphones = Reverse Loudspeakers

It is true that although they look nothing alike, a microphone and a loudspeaker actually have a lot in common. Just read a little bit on loudspeakers and you will realize they work the exact opposite way as a microphone. 

In fact, the parts of a microphone and the parts of a loudspeaker are almost exactly the same. One of the key components in both of them is simply a coil of metal wrapped around or sometimes, in front of a magnet. In a loudspeaker, electricity courses through this coil, creating a magnetic field. This magnetic field acts on the magnets causing the coil to move. Because the coil is attached to another part of the loudspeaker called the diaphragm or cone this part also moves. This movement causes air motion and this actually causes the sound waves that people can hear. How microphones work

Learn how a microphone turns sound energy into electrical energy:

 microphone working diagram

  1. Sound is just energy so when there is a noise such as your own voice the sounds waves created carry the energy (vibrations) towards the windscreen of the microphone.
  2. The diaphragm or cone is a very small piece of thin plastic inside the microphone and this part of the microphone moves back and forth when the vibrations hit it. 
  3. Because the coil and the diaphragm are attached they both move when the sound waves hit them. The coil, attached to the diaphragm, moves back and forth as well.
  4. The magnetic field is created because of the permanent magnet inside the microphone. This magnetic field causes an electric current to course through it. 
  5. Finally, that electric current that your microphone just created streams out to the sound recording device and you have just changed an original sound into electricity. This means you could potentially save the sound you have created forever or use an amplifier and a loudspeaker to make your sound energy even louder. 

 

Types of microphones

There are a few different kinds of microphones and although their basic purpose (to turn sound waves into electricity) is always the same, they achieve this in slightly different ways.

Ribbon microphones utilize two crimped ribbons of aluminum foil held tightly between two pole pieces. A permanent magnet placed below the ribbon causes it to vibrate back and forth when the sound waves hit. This, in turn creates an electric current to flow through the microphone. 

The microphone that was already described is referred to as a Dynamic Microphone. This is the kind you most likely think of immediately when you imagine a microphone. It uses the components mentioned earlier (diaphragms, magnets, and coils) to create an electric current. 

man holding microphone

The third type of microphone is called a condenser microphone. It contains the same parts but the diaphragm moves the metal plates of a capacitor instead of moving the coil as in the Dynamic microphone. A capacitor is two metal plates in close proximity to one another. 

Microphones may be omnidirectional or unidirectional. If you are recording something while there is ambient noise all around you it may be better to go with a unidirectional microphone as it picks up sound from only one direction. If you need your microphone to pick up sounds from all directions you will want to go with the more common omnidirectional microphone. As the name suggests, a microphone that is called a cardioid or hypercardioid will pick up noise in a heart shaped form. Another microphone that is aptly named is the shotgun microphone. As you may think, a shotgun microphone can pick up noise from a very precise location. Often referred to as radio mics, wireless microphones require an amplifier to transmit their electricity into sounds. 

You can learn more about the Saramonic Shotgun Mics here.

Intercoms

If you think about it an intercom must function as both a microphone and a loudspeaker. The most standard intercom can be used to both hear and speak to someone in a different room - think baby monitor or a desktop device allowing a parent to call their kids up for supper from the basement. Usually an intercom has handsets with a couple of simple buttons on them located in each room. The handsets can each function as both loudspeaker and microphone depending on which button is being pressed. 

For years the military has utilized the basic intercom to allow people easy access to speak with one another.  A person will simply push a button to talk and the microphone part of the device will be utilized, when the button is released the same device will work as a loudspeaker. The major problem with an intercom is the poor sound quality that is inherent when one device tries to serve opposite functions.

One of the benefits of using an intercom especially in public places is that they are much more difficult to break or vandalize. Often you will see an intercom instead of a regular telephone handset for use as an emergency device in elevators and in trains. Another important benefit is the ease of use. The pressing of a single button transmits a person's voice and the simple release of the button turns the intercom into a loudspeaker so whatever the person on the other end has to say is easily heard. 

To make it very simple to understand imagine a scenario in which a secretary is sitting in her office chair and needs to let her boss know that someone is waiting to see him. Instead of getting up and walking into her boss’s office she simply presses the button on the intercom. The boss’s intercom will then alert him with a sound such as a beep so he presses the button on his intercom, effectively turning his intercom into a loudspeaker and  allowing him to hear what the secretary has to say. She speaks into her intercom (which is functioning as a microphone at this point) and the sound waves are converted into electricity flowing into the boss’s intercom. As soon as the energy reaches into the loudspeaker it is converted back into sound waves. When he releases the button the process is reversed and the boss has a microphone that will change his voice into electric currents that travels through the copper wire back to his secretary still sitting in her office. 

Wireless intercoms

Although perhaps less scientifically interesting there are benefits to using an intercom without the hassle or tangle of wires or cables. Often, it is best to have both the loudspeaker and the intercom is its own handheld device. Other intercoms may work similar to broadband over powerlines in which the sounds are sent through the wiring in the rest of the house instead of utilizing its own wiring. 

An example of another wireless intercom that may be operated using home power lines are baby monitors. Baby monitors are placed in both the parent’s room and the infant’s room. The baby’s device holds the microphone so the parents can hear any sounds the baby might make and the parents keep the loudspeaker with them. Often the parents unit will both transmit the noise and light up to alert the parents of any problems. This type of unit does not require any wiring between them. 

You can view the Saramonic Wireless lav mics ranges here.

Make your own microphone!

What if you don’t have a microphone? Well, you are in luck because It is possible to use a regular earbud and very easily create your own. All you really need to do is plug the earbud headphones into a microphone socket! Now you have essentially reversed the function of the earbuds from acting as a loudspeaker into acting as a microphone. If you talk into your earbud it should amplify your voice. It’s kind of a cool trick, give it a try! Just a note of caution it may not work on your computer even though it works with your audio equipment. Sometimes one earbud will work as a microphone but the other will not. You will just have to try it and see. If it doesn’t work try adjusting your sound settings on the computer. There are some programs that will support your little experiment and some programs that may not.

If you want to use a microphone on your smartphone, then Saramonic have a range for iphones/ipads here, and a usb c compatible mic here.

History of Microphones

It was the inventor of the telephone, Alexander Graham Bell, who is credited with inventing the very first microphone in 1876. It was a basic contraption and not really all that useful as it required the sound waves to vibrate a needle in water. It wasn’t for another ten years that any improvement was made to this original microphone. Thomas Edison invented the first carbon microphone, which was much more practical. Edison's carbon microphone was actually used extensively in telephones and radio transmitters for decades, until the 1970’s in fact! In the 1970’s this long-standing design was finally replaced using piezoelectric ceramic elements. 

  1. M. Chorpening and F. H. Woodworth invented the first ceramic microphone way back in 1933. It was proven that an electric current could be created through the vibrations of  sound waves meeting the piezoelectric crystals. 

Although the carbon microphone had many uses it was not practical for things such as reproducing noise such as music. E.C. Wente of Bell Laboratories rectified this problem when he invented the condenser microphone in 1916. The condenser microphone allowed sound in motion pictures and the built in amplifier was perfect for radio broadcasting. 

In 1931 the dynamic microphone was invented by Wente and A. C. Thuras of Bell Laboratories. This is the type of microphone that we still use today because it’s design allowed for very little distortion of the sound. What a breakthrough! Our entertainment and communication possibilities would never again be so limited. 

Another microphone that was invented right around the same time, in 1931, was the ribbon microphone. This microphone was introduced by RCA (a major electronics company). The ribbon microphone is another important piece of technology. Despite being extremely heavy and easily damaged  we still use the ribbon microphone today especially for vocal recording and broadcasting because of the extremely natural sound it allows for.

References

https://en.wikipedia.org/wiki/Microphone

https://www.explainthatstuff.com/microphones.html