Understanding Audio – Part 1: The basic things you need to know

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Some say that humans are “wired for sound” and “the brain never stops listening” or, for those capturing audio for video, that “audio makes up 70% of the video quality”. So it’s no wonder why good sound is so important, but also why it’s a little daunting and complex for many, as there is a lot to know, and a tidal wave of product choices. So how do you cut through all the noise?


At Vistek we understand the importance of great sound, and offer a wide line-up of audio products, at an assortment of price points, ideally suited to a very broad range of audio applications. So whether you are just getting started with sound, or you just want to further improve your audio expertise, you can trust Vistek to help you understand how good, better and the best audio is captured, recorded, processed and delivered.

At Vistek we understand that it’s not just the quality of the image you record, but also the quality of the sound that matters!


Remember, there is no such thing as sound!

Did you know that what we refer to as sound (or audio), is actually created by pressure waves that are received by our ears and then interpreted by our brains as individual sounds? And like the waves on a beach, these pressure waves can be tiny ripples or huge and crashing.

Dynamic Range

Behringer XENYX 802 Mixer

Behringer XENYX 802 Mixer (click to view product)

The broad range of size and scope of the waves is what is referred to as dynamic range and every audio device has a lower and upper limit to the dynamic range it can handle.

When recording audio, these limits are controlled by using a mixer or recorder to set the upper limit of the signals dynamic range by capping it before it peaks.

When considering an audio product, it’s important to understand the limits, both high and low, of its dynamic range.

Frequency

Frequency refers to how often these sound waves come rolling in as well as how our brains interpret them. Lower frequencies are perceived as bass and high frequencies as treble.

It’s interesting to note that most people (with young, good ears and hopefully not too many loud concerts under their belts), can generally hear a frequency range of about 20-20,000 hertz (waves per second) and some animals can hear even higher frequencies.

Because prolonged exposure to extreme high or low frequencies can actually severely damage our ability to hear, audio equipment often limits the frequency response at both the upper and lower ends.

Noise

Just as wind noise, road noise, or people talking, or other background ambient sounds, can make it hard for you to pick out the voices or sounds you want to hear, electronic noise is inherent or can be induced into audio equipment, and it can drastically affect the overall sound quality and ultimately ruin the wanted sounds. This is a key spec to look for when choosing equipment.

Audio Levels & Gain

audio levels on a monitor

Watch your audio levels

The inherent way that microphones capture these pressure waves, or sound waves, and turn them into electronic waves is very subtle.

The signal levels produced at the microphone itself (know as mic levels) are quite low and it’s critical to protect them from any inherent or induced noise. Even a tiny amount noise can have a big effect on the final results.

To help control this, we can apply gain to, or amplify (boost), the electronic signals that the mic picks up during recording. This allows us to deal with/process the signals more effectively.

One important thing to remember is that any gain or amplification of wanted signal will also be applied to the unwanted noise during this process.

Higher levels are typically referred to as line levels, and because there are a myriad of standards for these, and we focus on the main two or most common standards, balanced versus unbalanced in our Understanding Audio – Part 2: Balanced vs. Unbalanced Audio Levels, Cables & Connections post.

Note: Line levels need to be protected as much as possible from unwanted noise and hum which can be caused by things such as nearby power cables (hum) or other external signals (RF radio frequencies) etc.

Common Mic Types & how to Mic Sources

The most important thing in miking any source is proximity, the closer the mic to the source the better, the better the levels and the lower the noise. So you need to learn miking techniques that allow you to best focus on the sources you want, with the tools you have available.

Another big tip, is that more is better! You can never have too much audio, the more sources and recordings you have, the better! Better backup, is also a great thing, and means you will never miss the important audio moment you want to capture, because missing the sound, is even worse than bad sound.


Recording 101: Microphones – RocketJump Film School

Video Description: Wondering which microphone would be best for your shoot? Kevin breaks down the basics so you can figure out the type of mic best suited for what you’re recording.

In this video, we cover how a microphone actually works, the difference between mic and line levels, XLR cables, pre-amps, phantom power, transducer types, and mic polar patterns.
More on recording techniques (and other equipment) later on in the series!


Dynamic, Condenser & Ribbon

There are three main types of mics, Dynamic, Condenser and Ribbon.

  • Dynamic mics are good rugged general use microphones
  • Condenser mics are slightly more sensitive, expensive and require external power (called Phantom Power) or battery power to operate, they are better for more detailed sounds and still generally robust.
  • Ribbon mics are typically very expensive, but are the best at capturing subtle nuances in voices and music but are also much more fragile so usually only found in the studio.

Omni vs Cardioid

There are also two main types of mic pickup patterns, Omni Directional which is the most common and picks up a broad pattern, virtually everything around it. Cardioid or “Unidirectional” which pickup a more focused forward pattern, reducing unwanted sound from the sides and rear of the mic. There also Hypercardioid and figure 8 pickup patterns for more specialty applications.

4 Common Mic Types

Sennheiser MKE600 Shotgun Mic

Sennheiser MKE600 Shotgun Mic (Click to view product)

There are basically four common styles of microphones.

  • Lav or Lavalier type for pinning on or near a subject.
  • Hand or handheld, mostly for vocals, interviews & presentations etc. either handheld or on a stand
  • Shotgun a tubular shaped mic, used on camera or on a boom, which has a very focused Hypercardioid or shotgun pattern, hence the name, for pointing at your sound source
  • Large Diaphragm type, larger desk or studio style, used mostly for vocals.

A unidirectional or Cardioid mic is great for live presentations & vocals and also stand-up interviews as it cuts crowd and ambient noise, just be sure it’s pointed at the source you want when you want to hear them.

One important thing to remember about a Shotgun or Hypercardioid mic is that it is creating a focused tunnel like pick up pattern, but that pattern does NOT stop at your talent, so you have to be mindful of sources behind your talent, a jackhammer or screaming audience in the background for example can easily wipe out your talents voice.

Wireless

Saramonic UwMic9 DTLK - Dual TX LAV Kit - UHF Wireless Mic System

Saramonic UwMic9 DTLK – Dual TX LAV Kit – UHF Wireless Mic System (Click to view product)

Another style or variation is called wireless which basically by design just eliminates the cables but could potentially used with any type of mic with any type of pick up pattern. But most often with a Lav, Handheld or Shotgun Omni or Cardiod. Wireless simplifies things by letting the talent or the camera operator to roam freely, uninhibited by wires.

There are a broad range of wireless system possibilities and technologies which we will cover in more detail in another article.

Hum and feedback

Hum and feedback are the two most common announces in any audio.

Hum is caused by having a grounding issues where the 60hz power line frequency is somehow bridging into the system because audio systems are joined across 2 or more power circuits that have improper grounding. You can either use AC ground plug lifts on the equipment or purchase devices called “hum bucking coils” to eliminate this issue.

Feedback is caused by having the audio source amplified into a mic that is picking it up, creating basically and endless loop, speaker talent position and mic selection have a lot to play here in eliminating feedback.

Typically try to have the speakers slightly to the front and sides of the talent, and use a Cardioid or unidirectional mic or use a Lav or headset mic so it’s very close to the sound source. Some mixers and external boxes can also enable a process called feedback reduction.

Pre Amps and Gain

One of the things to clearly understand is that whatever Mics you use, the level you are working with has to be boosted or gained, or amplified, and processed in order to be recorded or sent through a PA (Public Address/speaker) system.

Obviously in a device like a camera designed predominantly for still photography the audio circuits are the lowest priority of the manufacturer. That’s why it’s often best to record externally on a dedicated audio recorder and post sync your sound. Even with higher end broadcast and cinema production cameras, on a major productions, they typically have a separate team or crew, and separate recording for all of the audio because of it’s high importance.

Compressors, EQ or Equalization – filters and Wind

A compressor basically is a kind of auto leveler, ideal for voices it helps to smooth out the levels so they don’t rise and fall to much and maintain a good consistent level overall.

Essentially, there are two types of EQ, Graphic and Parametric – with Graphic being the most common. With graphic you are given a preset selection or range of the audio frequencies, say low, mid, and high, for example and can provide a boost or cut of those ranges of frequencies.

A Parametric equalizer allows more subtle and specific control by allowing you to pinpoint specific frequencies to boost or cut or making broad changes to groups of frequencies.

You may also have filters that will affect a set part of the frequency range for example low cut filters are common on mics to lower rumble, wind, and handling noise. You may also encounter high frequency filters as well that can reduce hiss and other unwanted high pitched sounds.

Other devices to help lower wind noise is the common foam sock on a mic or the infamous (dead cat) hairy fur like cover, for covering the mic out in the wind. Remember though that these are designed for wind so ideally don’t use them if recording indoors as thy can limit some of the response of the mic.

Digital vs Analogue

Microphones are obviously completely analogue devices the way they capture and convert the pressure waves into electronic waves is completely analogue. Once we have created the analogue sound wave we can choose to process and send it in a digital domain. The great thing about digital is that is does not suffer from analogue generational loss, it can be moved and re-recorded digitally with no increase in noise.

Zoom F6 Field Recorder

Zoom F6 Field Recorder (Click to view product)

But a lot of the quality of a digital sound comes down to the sampling rate, and the sampling bit depth.

Today most the most common bit depth is 16 bit, which is the resolution of graph plot points of the audio analogue wave. Of course because audio is complex with subtle nuances this might not be enough to accurately capture or represent the audio you are recording, especially for sourcing and mastering.

Many higher quality cameras and recorders now support 24 Bit which provides better resolution of sound and some specialty recorders even offer up to 32 bit floating point which amazingly allows for you NOT to have to ride signal levels in acquisition because no matter the dynamic range or peaks it can adequately represent the signal.

The sampling frequency is also important, most often 44.1 khz (transmission & CD) or 48khz for video or 96khz for high end audio production & editing. The sampling frequency is the amount of samples taken per second. Obviously the more samples taken the better the quality of the sound.

Latency

Datavideo AD-100M Audio Delay Box with Microphone Input

Datavideo AD-100M Audio Delay Box with Microphone Input (Click to view product)

Latency or delay is common in audio because audio travels slower than light and slower than therefor video. Also many cameras are optimized for recording, not live production and there can be many frames of delay in the video and even more, or perhaps less, in the sound, depending on how and where it is routed from, and this latency also gets compounded in both processing and transmission.

Typically only a 2+ frame delay is noticeable to a viewer.

Good news is for those that need it. There are audio delay and sync boxes that can re-time or re-clock the audio and video so that it remains in sync.

Summary

All of this points to literally hundreds and hundreds of variations and also quality (build) levels for both microphones and audio equipment overall. Usually anyone working with audio would invest in a selection or variety of these mics, and other audio equipment, so they have the right tool for the right application.

So remember what is important to you is, the pattern, or pickup direction, the operation dynamic or powered, the robustness, the style, is it suited to your application, and of course finally the sound quality itself vs your budget. Then there is all the other equipment behind the mic to consider.

Of course the popularity of a particular mic or product can be a good indicator of its sound quality for a given cost, but where you can we advise you test for yourself.

Again on the topic of budget, it does not make sense based on the importance of sound quality overall, to spend a lot on a camera and then go low budget with your audio equipment, both play important roles and deserve to be properly considered!


Cover Image Credit: Jason Rosewell on Unsplash

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