ccurtis
Well-Known Member
In a light organ, the amplified signal from a microphone, or audio line output, is applied to a controller that subsequently drives the light intensity of a light source(s) for the purpose of adding a dimension of sight to the music listening experience. In most designs the goal is to have the light intensity rise is direct (linear) proportion to the amplified audio signal.
I have developed, built, improved such light organs of various configurations and designs over the past several years. However, while listening to music and observing the lights varying in brightness, accordingly, I was never truly satisfied with the effect. When I heard the peaks in the music and did not experience the peaks in light brightness in the same way I heard them. Sure, the light was brighter, but my sense of the increased brightness was not the same as my sense of the music. Additionally, there is too noticeable brightness fluctuation at times when the music is not so dynamic.
Some time ago, I attempted to address this (https://www.electro-tech-online.com...ut-driving-pwm-led-loudness-indicator.156838/). Still not satisfied, I recently realized I got the math wrong.
It is true that the way we perceive sound pressure is not the same as the way our eyes perceive light intensity and that is reason for the dissatisfaction. Stevens' Power Law tells us that the exponent for human sound perception has an exponent of 0.67. It also tell us that the exponent for human light perception is 0.33. Not the same!
So how do we get them to match? That's where the math problem comes in. Setting the two expressions equal gives us:
S^0.67 = L^0.33 (S is the sound pressure stimulus, or voltage from the microphone) (L is the light intensity)
Rearranging:
S^(0.67/0.33) = L or S^2 =L
Therefore, L corrected = L^2. In other words the signal driving the lamps must be squared! The goal is NOT to linearize the light intensity except only to provide a linear signal that is subsequently to be squared to give the desired result.
Now, finally, the eye sees what the ear hears.
I have developed, built, improved such light organs of various configurations and designs over the past several years. However, while listening to music and observing the lights varying in brightness, accordingly, I was never truly satisfied with the effect. When I heard the peaks in the music and did not experience the peaks in light brightness in the same way I heard them. Sure, the light was brighter, but my sense of the increased brightness was not the same as my sense of the music. Additionally, there is too noticeable brightness fluctuation at times when the music is not so dynamic.
Some time ago, I attempted to address this (https://www.electro-tech-online.com...ut-driving-pwm-led-loudness-indicator.156838/). Still not satisfied, I recently realized I got the math wrong.
It is true that the way we perceive sound pressure is not the same as the way our eyes perceive light intensity and that is reason for the dissatisfaction. Stevens' Power Law tells us that the exponent for human sound perception has an exponent of 0.67. It also tell us that the exponent for human light perception is 0.33. Not the same!
So how do we get them to match? That's where the math problem comes in. Setting the two expressions equal gives us:
S^0.67 = L^0.33 (S is the sound pressure stimulus, or voltage from the microphone) (L is the light intensity)
Rearranging:
S^(0.67/0.33) = L or S^2 =L
Therefore, L corrected = L^2. In other words the signal driving the lamps must be squared! The goal is NOT to linearize the light intensity except only to provide a linear signal that is subsequently to be squared to give the desired result.
Now, finally, the eye sees what the ear hears.