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.
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.
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