At some point almost every videographer will run into a situation where the subject they want to record is a considerable distance from the camera. There are a wide array of lenses that do a fantastic job of capturing great visual images from amazing distances. But capturing audio that matches those great visuals can be a real challenge. A great video with bad audio will not be watched.
There are several options for capturing long-range audio, here are the top 5:
#1 Wireless microphones
Wireless microphones are widely used. A wireless is a matched set of radio transmitter and receiver. The transmitter is added to, or connected to a standard microphone which captures the audio from a nearby source. The microphone converts the sound energy of the audio to an electrical signal and that signal is transmitted to the receiver which is located at the camera or audio mixing board. The distance between the two can be hundreds of feet, while eliminating the microphone cables.
Advantages of wireless microphones include:
Wireless microphones allow the user to move around freely without being tethered to a microphone cable.
Wireless microphones can be used in a variety of settings, including live performances, presentations, and interviews.
Wireless microphones can be easily set up and used without the need for cables or other equipment.
Disadvantages of wireless microphones include:
- Limited range
Wireless microphones typically have a limited range and may not work well in large or crowded spaces.
- Battery life
Wireless microphones rely on batteries, which may need to be replaced or recharged frequently.
Wireless microphones may experience interference from other wireless devices, such as Wi-Fi routers or cell phones.
Wireless microphones can be more expensive than traditional wired microphones.
Wireless microphones are vulnerable to hacking and eavesdropping if not properly secured.
#2 Shotgun microphones
Most people are familiar with a shotgun microphone. They are seen wherever you see a video camera. Shotgun mics are actual a standard microphone element, or diaphragm inside of, or at the end of, a long hollow tube. That hollow tube, called an interference tube, focuses the sound so that it’s only capturing sound from what’s directly in front of it. There’s no mechanical amplification. They rely solely on electronic amplification. It will be up to your amplifier, recorder, etcetera to amplify the signal captured by that microphone element.
Advantages of shotgun microphones:
- Relatively Inexpensive
You can get extremely expensive ones, but there are many that are much more reasonably priced as well.
- Relatively Small
You can mount them to cameras. You can easily transport them.
- Natural Sound
High quality shotgun mics provide a very natural sound as long as your subject is directly in front of the microphone (so the sound isn’t going through the interference tube).
Note: If the sound is off-axis, the sound will become “colored” and not as high quality.
Disadvantages of shotgun microphones:
- Not As Directional as Expected
For the normal human voice frequency range, they’ll go up to 60 or 70 degrees off center-line before you see a significant fall-off (of the microphone picking up the noise).
- Strictly Electronic Amplification
In order to amplify what the microphone is picking up you’ll have to increase amplification electronically (no natural amplification) which leads to the self-noise (“hiss” and “hum” ) that is present in all electronic amplification.
#3 Parabolic microphones
A parabolic microphone is the combination of a microphone and a parabolic collector. A parabolic collector has a very special shape so that all the sound entering that dish from directly in front is focused to a single point, which is where you put your microphone. This provides a “mechanical” amplification as opposed to electronic.
A parabolic mic is very directional. The directionality is created by the difference in amplification it provides. Sound coming from in front of the parabolic is amplified, but what is off to the side, or behind the dish, is not amplified and is actually deflected to a certain extent by the dish.
You can use a wide array of standard microphones within the parabolic collector but omnidirectional pickup patterns are normally used.
Advantages of parabolic microphones:
- Very Directional
For normal frequency ranges you’ll find a significant drop-off (in sound pickup) at 30 or 40 degrees off center-line. At extremely high frequency ranges it will be as narrow as 5 degrees off center-line. It’s at least twice as narrow of a listening pattern as a shotgun microphone.
- Significant Natural Amplification
Again the natural sound amplification doesn’t have the “hiss” or “hum” self-noise of electronic amplification. Additionally, everytime you double the size of the dish you quadruple the amount of amplification you’re getting. This is why the 26” KLOVER MiK gets ~45x sound amplification and can be used at NFL games even from the sidelines.
Disadvantages of parabolic mics:
- Relatively Large
Yes, you can get smaller parabolic microphones (even down to the 9-inch KLOVER MiK), but you get less amplification at those smaller sizes. So if you’re desiring large amplification you’ll need a larger and more unwieldy dish.
- “Colored” Audio
Parabolic mics have a bias toward the high frequencies because the low frequency sound waves are absorbed into the dish more than high frequencies are. This means that there is an over-emphasis on the higher frequencies in the final recording.
This “colored” audio is usually not immediately recognizable by the lay-person’s ear (though a sound-engineer might be able to pick up on it). However, parabolic mics will probably never be used to capture music or shoot a movie where you want the highest possible sound quality. That being said, they are used by news reporters without the listening audience being able to tell. In addition, the high frequency bias is relatively linear, so it can be easily corrected in post-production through equalization if necessary.
#4 Microphone arrays
A microphone array is a collection of multiple microphones arranged in a specific pattern or configuration. The signals from each microphone are then processed and combined in order to improve the overall audio level (amplification) or to extract specific information from the sound.
A microphone array provides a mechanical amplification, similar to a parabolic collector, because you’re taking a large number of elements with a low application and combining them to get a larger amplification.
The directionality, or focus, of the microphone array is done through electronics. A computer or digital signal processor takes all the different microphone elements and adds or subtracts the signals to focus on what’s in a particular direction or location relative to the array. This electronic processing looks for microsecond delays between one signal and the next to determine where that sound source is coming from.
Advantages of microphone arrays:
- Super Focused
They can focus in on a specific sound source using their computing power and microsecond delays from their microphone elements.
- Mechanical Amplification
Since it’s essentially adding together the different microphone element recordings to create the amplification, you don’t get the self-noise of electronic amplification.
Disadvantages of microphone arrays:
You’re essentially buying multiple microphones all put into 1 custom array, and are also required to supply the necessary computing power.
Because they require extensive signal processing, down-time, maintenance and upgrades are to be expected.
#5 Laser microphones
These microphones use a laser beam to pick up sound vibrations from a surface, allowing them to capture audio from a distance without actually being physically near the sound source. You may have seen a laser microphone in a spy movie, or television show but they are not widely used.
A laser is pointed on a flat surface, usually a window pane, that moves slightly as a result of the sound pressure applied to it. As that laser beam is reflected back to its source, the movement of the laser beam generates an electronic signal that is converted to an audio signal.
Advantages of laser microphones:
- Extreme Distance
The laser can shoot extremely long distances, so as long as the laser can be shot out and reflected back, audio can be picked up. (Lasers are shot to the moon and back to measure the distance!)
Disadvantages of laser mics:
- Precise Setup
The further away you are from the reflective surface, the more critical the alignment becomes. You must be able to send the laser and capture it again after it bounces off the surface. If you’re out of alignment you’ll capture nothing. If you are misaligned by one half of a degree, a laser traveling a hundred yards and back will be over five feet off of its expected position. In addition, if the path of the laser gets blocked no signal will be captured.
The laser emitter, receiving, and computing power must all be purchased to have a working laser microphone.
We’ve covered the common ways to capture long-range audio. They are wireless mics, shotgun mics, parabolic mics, microphone arrays, and laser microphones. Each of these options have Advantages and Disadvantages. The choice that is right for you depends on your particular situation. If you would like to discuss your particular needs in capturing long-range audio, use our Contact Us form to reach out. We love to help.