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There’s nothing more frustrating than picking up background noise, right? With this in mind, the main reason to use a directional microphone is to reduce and/or remove unwanted noise and focus on the desired sound source. For example, if you are recording an interview in a noisy environment, use a highly directional microphone that can reject sounds coming from behind or beside the speaker. This way, you can capture their voice more clearly and avoid picking up distracting background noises!

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Another common technique is using an interference tube before the diaphragm. This long tube with slots along its length allows sound waves to enter at different angles. The sound waves interfere with each other inside the tube and create different patterns of pressure on the diaphragm depending on their direction. This way, sounds from directly in front of the tube are relatively unaffected (not amplified as some believe), while sounds coming from other directions are attenuated.  A microphone with an interference tube is commonly referred to as a “shotgun” microphone.

Standards for the sign design and application of the signs shown here as well as for other traffic control devices are contained in the Manual on Uniform Traffic Control Devices (MUTCD). Dimension drawings for signs can be found in the Standard Highway Signs book. Both of these books are available in electronic format online at https://mutcd.fhwa.dot.gov. This web site also contains information on standard lettering used on highway signs and pavement markings and on highway sign color specifications.

Roadway signs in the United States increasingly use symbols rather than words to convey their message. Symbols provide instant communication with roadway users, overcome language barriers, and are becoming standard for traffic control devices throughout the world. Familiarity with symbols on traffic signs is important for every road user in order to maintain the safety and efficiency of our transportation facilities.

Prepared in 2002 by the US Department of Transportation Federal Highway Administration Office of Transportation Operations

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A directional microphone is a microphone that picks up sounds primarily from a specific direction.  An omnidirectional microphone is not considered to be directional.  The more focused a microphone is on one particular direction, the more directional it is.

For More Information: https://mutcd.fhwa.dot.gov/ Contact Information: Kevin Sylvester at Kevin.Sylvester@dot.gov

A directional microphone uses different techniques to manipulate how sound waves reach its diaphragm (the part that vibrates in response to sound). Depending on how the diaphragm is designed and positioned, it can be more or less sensitive to sounds coming from different directions.

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Before we go over what a directional microphone is, let us first go over what microphone directionality is. The directionality of a microphone is the direction(s) from which a microphone can pick up incoming sound. Sounds can come to a microphone from all directions – the front of the microphone, the back of the microphone, or the sides – and a microphone will pick up these sounds differently based on its directional characteristics or directionality. A microphone can pick up sounds with high sensitivity coming into the front of it but not sounds to the sides and rear. Another microphone may pick up sounds well from the front and rear but not the sides. Another may pick up sounds well from all sides. There are many different combinations.

As we have seen, a directional microphone can offer many benefits for audio recording, such as noise reduction, sound isolation, and spatial enhancement.  Another advantage of a directional microphone is that it can help to reduce feedback. Feedback is the annoying squealing sound that occurs when a microphone picks up its own output from a speaker or monitor.  Since a directional microphone is more sensitive to sounds coming from a specific direction, it can be located closer to a speaker or monitor without feedback as long as it is pointed AWAY from the speaker.

Sign shape can also alert roadway users to the type of information displayed on a sign. Traffic regulations are conveyed in signs that are rectangular with the longer direction vertical or square. Additional regulatory signs are octagons for stop and inverted triangles for yield. Diamond-shaped signs signify warnings. Rectangular signs with the longer direction horizontal provide guidance information. Pentagons indicate school zones. A circular sign warns of a railroad crossing.

Hard copies of the MUTCD can be purchased from the American Association of State Highway and Transportation Officials (http://www.aashto.org); the Institute of Transportation Engineers (http://www.ite.org); the American Traffic Safety Services Association (http://www.atssa.com); and the US Government Printing Office (http://www.gpo.gov). The Standard Highway Signs book can be purchase from the US Government Printing Office and the American Traffic Safety Services Association through the web sites listed above.

Another reason to use a directional microphone is to create a sense of space and depth in your recordings. For example, suppose you are recording a musical performance with multiple instruments. In that case, you can use different types of directional microphones to capture different aspects of the sound. You could use an omnidirectional microphone to record the overall ambiance of the room, a bidirectional microphone to record the stereo image of the main instrument, and a cardioid microphone to record the vocals or solo parts. By mixing these different tracks together, you can create a more realistic and immersive sound experience. Perfect!

If you are interested in audio recording, you may have come across the term “directional microphone”. But what does it mean, and why is it important? In this blog post, we will explain what a directional microphone is, how it works, and its advantages and disadvantages.

However, it also has some drawbacks you should know before choosing one.  A directional microphone can produce a less natural sound than an omnidirectional microphone. Since a directional microphone rejects sounds coming from certain directions, it can also lose some of the natural ambiance and reverberation of the recording environment. This can make the sound more dry and dull, especially if you are recording in a large or acoustically rich space. To compensate for this, you can use an omnidirectional microphone as a secondary source to capture the room sound and blend it with the directional microphone signal.

To learn even more about directional microphones, we suggest Arthur Fox’s article, “A Complete Guide To Directional Microphones (With Pictures)”.

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For a more comprehensive explanation of these pickup patterns refer to our article: “What Are The 5 Most Common Microphone Pickup Patterns?”.

Test your Sign IQ by taking the interactive shape and color quiz available on the web at https://mutcd.fhwa.dot.gov. On the navigation bar under Knowledge, select Sign Shape/Color.

To learn more about the different types of microphone, please refer to our article, “What Are The 3 Most Common Types of Microphone Construction?”

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**The use of coral for incident management signs was anticipated for inclusion in the 2003 edition of the MUTCD at the time of this printing.

A directional microphone is a microphone that picks up sounds primarily from one specific direction and it can help reduce noise and isolate sound sources. However, it can also have some drawbacks, such as unnatural sound quality. Therefore, you should always consider your recording goals and environment before choosing a directional microphone.

The color of roadway signs is an important indicator of the information they contain. The use of red on signs is limited to stop, yield, and prohibition signs. A white background indicates a regulatory sign; yellow conveys a general warning message; green shows permitted traffic movements or directional guidance; fluorescent yellow/green indicates pedestrian crossings and school zones; orange is used for warning and guidance in roadway work zones; coral is used for incident management signs;** blue indicates road user services, tourist information, and evacuation routes; and brown is for guidance to sites of public recreation or cultural interest.

One common technique is to add ports on both sides of the diaphragm. Sounds that come from both sides, which are most often background buzz, cancel each other out and allow the listener to concentrate on sounds coming from one direction. The most advanced directionality comes from using multiple microphones.

The way that a microphone captures sounds from these different directions is called its pickup pattern.  Not sure what this is? Don’t worry! We’ve included a list below of the most common types of microphone pickup patterns.