The 'Awe' behind Octave

One word, two different meanings ! Encountered this before ? I am sure you should have. In fact the Probability is high if you are even remotely related to the Audio / Music. One such term is the 'Octave'. An Octave assumes different meaning under different circumstances and usage. 'Octave' for a Musician is different from Octave for a Sound / Acoustics Engineer which is again different from Octave for a Casual Music Lover !

Octave Originates from a Latin word "Octavus". 'Oct' denotes 8. And Eight is an all important number for all musicians across the world, right from your Classical version (Sa-Re-G-Ma-Pha-Dha-Ne-Sa) to your Western Version (C-D-E-F-G-A-B-C).

In Pure Music, the Octave is the interval between two different frequencies in the ratio of 2:1. In other words, a One Octave rise from 125 Hz is 250 Hz. A One Octave Fall from 600 Hz is 300 Hz. Similarly, a two Octave rise from 4 Khz is 16 Khz. The Complete Musical Scale is generated by defining one Frequency and working out all other musical notes with sharps, Flats, etc.. from that defined frequency.Example if my note A is 440 Hz, i can go from 440 Hz to 880 Hz in the same Octave. From 880 Hz the second Octave Starts and ends at 1760 Hz, so on and so forth ! Confusing ? well, wait till we get to the Audio part of the story :)

In an all Audio world, there is nothing to enjoy, there are no emotions and sentiments, however there is a lot of numbing science. For Starters, the Octave in audio, is the interval between two frequencies which are in the ratio of 10^0.3 to 1. Unlike Music where boundaries are constantly pushed, Audio always starts with well defined boundaries. One of those boundaries is called Reference. Most Audio philosophies are formed with a set reference. Like in this case, the Reference Frequency of 1 Khz are taken as a base and other Frequencies above and below this set frequency are calculated. A 1 Khz frequency will have a octave of 10^3.0. When this 1 Khz is extrapolated either ways;

10^1.5
10^1.8
10^2.1
10^2.4
10^2.7
10^3.0 (Base Freq)
10^3.3
10^3.6
10^3.9
10^4.2

Now a simple log calculation of these numbers will get you the decimal representation as follows;


10^1.5 - 31.6 Hz
10^1.8 - 63.1 Hz
10^2.1 - 125.9 Hz
10^2.4 - 251.2 Hz
10^2.7 - 501.2 Hz
10^3.0 - 1000 Hz
10^3.3 - 1995 Hz
10^3.6 - 3981 Hz
10^3.9 - 7943 Hz
10^4.2 - 1585 Hz


 Coming back to real world, you must have wondered when choosing a simple graphic Equalizer in your Source / Processing Units, why does the Equalizer show only specific bands of frequency. Like Say 80 Hz or 125 Hz or 1 Khz. If you observe carefully you can notice that most of the daily use equalizers have the following set of values to tweak around.
31 Hz
63 Hz
80 Hz
125 Hz
250 Hz
500 Hz
1 Khz
2 Khz
4 Khz
8 Khz
16 Khz

These are nothing but rounded off values of the figures we have arrived earlier. They are called 1 Octave Eq bands.

Few Sources and processors are capable of 1/2nd, 1/3rd Octaves also. Some of the of high end, studio use mixers, Equalizers, Real Time Analyzers have ability to split into 1/6th or 1/12th Octave too.

A simple rule to remember;
1 Octave will have 10 Bands
1/2 Octave will have 20 Bands
1/3 Octave will have 30 Bands
1/6 Octave will have 60 Bands
1/12 Octave will have 120 Bands.

So that concludes today's post. Octave is a very important word in the world of Music and Audio. Same Word, Almost the same meaning, but different usage and varied applications.        

The Music in the Audio

Greetings Audio enthusiasts, Friends and fellow Bloggers,

As a part of first blog entry under Monaural Musings, let me narrate a small incident that made me realize the difference between Music and Audio.
During my early days, i used to go for Flute Classes. My Guru was a jack of all trades, which basically means when he is out for break, me and my companions have the opoourtunity to try out all different instruments from Harmonium, to Jazz Pads. There is always a thrill in trying to do something which you are not supposed to do. Although we had strict instructions not to touch other instruments, we seldom cared a bit about that piece of advice. There were many instruments, few which will make a sound when you hit it randomly (Like the Guitar), few which wont budge (Like the Sax) whatever you do. However, i had taken a special liking to one instrument - The Drums. I like them a lot for two reasons, the Drum kit was by itself huge, making its presence felt in a macho way among rest of its puny peers. Secondly, i loved the thump, kick and snare of the drums. There was one hunk who would come to practice drums. When in full flow, i would just stop whatever i was doing to watch the action. It was pure 'eargasam'. The Music filled my mind and soul. There is nothing more i can ask for when i hear this kind of music.

Long afterwards, we brought our first Hi-Fi System - From Phillips. I was long fascinated by the Knob controls of Tone and Stick Controls of  Equalizers, and when i got my hands on them, i was already fiddling with it. The one we got had a 3 Band Eq - Bass, Mid and Treble. I always loved to push the Bass up to experience the thump and Kick. Few songs got them right. Few songs played them ok. Few songs sounded downright crap. I didnt understand. Why is the Sound of a Drum appear so different in different songs. Why isn't the same kick and punch replicated for all songs of the same genre ?

I took me quite a while to understand that the sound you hear out of an HI-Fi system has many variables to it few controlled and a lot uncontrolled. I was beginning to understand that, Audio is different from Music. I realized why Composers are called Musicians and Programmers are called Sound Engineers.
Audio is Science -  The way a sound is recorded, the way sound is played, the way sound reaches your Tympanic cavity.
Music is Emotion - The way you sink your senses, the way goosebumps standup your skin, the way you forget everything else.   
Perhaps it would be fair to draw an analogy and compare Audio and Music with your Mind and Heart.
Audio like your Mind is about asking logical questions, needing rationale to proceed and making you look like a School HeadMaster.
Music like your Heart, doesn't need Justifications, Clarifications or Classifications and makes you look like a Toddler.

Always Enjoy the Music and Reason the Audio - But, don't do both at the same time.


Cheers
Praveen