Audio

Correlation of File Size and Audio Quality

nate@audiosyntax.net

There was once a time when we really needed to pay attention to disc space and file size when it came to recording. Writing those log sheets is a thing of the past with the plethora of HD space now available at a relatively cheap price. However, I routinely look back on the correlation of file size and audio quality for various reasons. Usually when I begin a recording project I like to dedicate an entire hard drive to the band or project. Using the below  calculations I can generally determine the size of the hard drive needed to fit the project. Nowadays I tend to find myself always buying 2TB hard drives which will fulfill any project. If I waste the space, it doesn’t matter. Either way, these calculation tables are great for any engineer to have on hand.

All the calculations for high resolution audio below are for the Pulse Code Modulation audio format. Regularly referred to as PCM, it  commonly uses the file extensions .wav or .cda. There are quite a few other combinations of bits per sample and samples per second which may be used as well as a large number of containers and file extensions. Tables below refer to calculations based on the most common mono and stereo settings used by engineers. Calculations for MP3 files are based on the LAME audio encoding standards. They also include both left and right stereo channels because who the hell makes Mono MP3 files? But the again who records at an 64 Kbps? Kbps means “Kilobits per second” (1,000 bits per second) and KB means KiloBytes (1,000 Bytes). There are 8 bits in a byte. Note the uppercase “B” for bytes in “KB”. A lowercase “b” (Kb) would indicate bits.

The exact file size below will vary from system to system likely due to differences between binary and decimal counting systems (multiples of 2 versus multiples of 10). Check out my Base-2 Methodology post to get a better explanation of this confusing phenomenon. The file header information and ID3 tags (for MP3s) will have an effect on the numbers. Album cover art tends to affect these numbers the greatest as images can commonly be 2MB or larger. These numbers should be used as a “ballpark” amount.

Mono WAV (single channel)

Settings Bitrate File size
per second		 File size
per minute		 File size
per hour
16 bit, 44.1 KHz 705.6 Kbps 88.2 KB 5.292 MB 317.52 MB
16 bit, 48 KHz 768 Kbps 96 KB 5.750 MB 345.60 MB
24 bit, 44.1 KHz  1058 Kbps 132.3 KB  7.8 MB 465.1 MB
24 bit, 48 KHz 1,152 Kbps 144 KB 8.640 MB 518.40 MB
24 bit, 96 KHz 2,304 Kbps 288 KB 17.280 MB 1.0368 GB

 

Stereo WAV (dual channel)

Settings Bitrate File size
per second		 File size
per minute		 File size
per hour
16 bit, 44.1 KHz 1,411.2 Kbps 176.4 KB 10.584 MB 635.04 MB
16 bit, 48 KHz 1,536 Kbps 192 KB 11.520 MB 691.2 MB
24 bit, 44.1 KHz  2,117 Kbps  264.6 KB 15.5 MB 930.2 MB
24 bit, 48 KHz 2,304 Kbps 288 KB 17.28 MB 1.036 GB
24 bit, 96 KHz 4,608 Kbps 576 KB 34.56 MB 2.0736 GB

 

Stereo MP3 (dual channel)

Bitrate File size
per second		 File size
per minute		 File size
per hour
64 Kbps 8 KB 480 KB 28.8 MB
96 Kbps 12 KB 720 KB 43.2 MB
128 Kbps 16 KB 960 KB 57.6 MB
160 Kbps 20 KB 1.20 MB 72.0 MB
192 Kbps 24 KB 1.44 MB 86.4 MB
256 Kbps 32 KB 1.92 MB 115.2 MB
320 Kbps 40 KB 2.40 MB 144.0 MB

Understanding Microphone Polar Patterns

nate@audiosyntax.net

What are Polar Patterns?

Polar patterns describe how a microphone picks up sound. Specifically, it is a standardized measurement that describes the sensitivity of the microphone from all directions. The polar pattern is one of the most important specifications for a microphone and can be helpful determining the right microphone for the job as well as achieving optimal performance.

Each microphone has it’s own polar pattern which is unique to its design and characteristics. However, most polar patterns can be placed into 5 different categories of microphones. Although there are many other poplar pickup patterns found in microphones I will only cover what I feel is the most common and can still be applied to microphones that you might sometimes place in a different category of polar pattern. I’ll describe the five most common microphone polar patterns found in the industry today.

Omni-Direction

Omni microphone pick up from all directions equally. The pattern is usually represented by a full circle. Commonly found in lavalier and lapel microphones for TV and film as well as hi fidelity studio situations and measurement tools.

Bi-Directional

Bi-Directional microphones are also sometimes called figure 8 microphones. Sound pickup is equally sensitive in the front and back of the microphones. The sides of the microphone will generally have a high rejection of audio which makes this style of microphone perfect for precise application. The polar patter resembles an 8 and shows equal pickup on opposite poles of the microphone. Most ribbon microphones are bi-directional and almost only used exclusively in the recording studio environment.

Cardioid

The most common pickup pattern is undoubtedly the cardioid microphone. Strong presence in the front of the microphone with a -6db drop at 90 and 270 degrees respectively. This is an ideal pattern for any broad use microphone and can be used in any situation and has excellent gain before feedback. The polar pattern is represented by a heart shape and is one of the most common styles for microphones.

Super-Cardioid

These microphones usually have a specific use in film and TV. They are more directional than cardioid microphones but also pickup directly behind the microphone at 180 degrees while having a steep roll-off of sensitivity on the sides. Commonly found in shotgun microphones and the pattern tends to look like a mushroom.

Lobar

Lobar pattern is also commonly called shotgun pattern because you generally only see this polar pickup pattern in shotgun microphones. These microphones are as unidirectional as it gets and are intended to block as much background noise as possible. The polar pattern is represented by what looks like a stick and is much thinner than a figure 8 polar pattern.

Introducing…

nate@audiosyntax.net

Audiosyntax Productions

Let me explain a little bit about who I am and what Audiosyntax is all about. Audiosyntax Productions is a comprehensive audiovisual communications company in Indianapolis, Indiana. We specialize in onsite multimedia services and logistics for event and stage productions. Established in 2005, Audiosyntax Productions LLC has played a part in the success of many small businesses, traveling artists, stage shows and corporate events in the Midwest.

Chief audio engineer and technician Nate Sparks has an elaborate background of audio and video system technologies and has over 10 years of professional experience in the studio and on the stage as an audio mix engineer and producer. Nate takes deep pride in the service he provides and will be sure to make your next project a success.

Nate Sparks in Studio

Audiosyntax Productions offers a variety of services all related to audio/video technologies for home and business. We offer multi-track recording services, studio production and engineering, live sound system installations and operation, as well as technology consultations and repairs. Audiosytax Productions LLC also offers a large range of IT related services for support of the latest IP/AV integrated technologies including CobraNet and Dante.

Check out our SERVICES page to see a larger list of the services we offer. Occasionally we will offer services that are not listed on the website so do not hesitate to contact us if your need is not listed. Many of our services are customized based on the details of the project. Each customer is different so we will be glad to talk you through your project and find a solution that works. You can contact us by using the form provided on our CONTACT page.