There are three parameters of this filter that are described in the phrase "100 Hz 12 dB per octave low pass filter". I'll cover them in reverse order.

• Low pass filter - This means the filter does not change lower frequencies ("passes" those frequencies through) and blocks higher frequencies. Sometimes these filters are called "high cut filters", but that can get confused with a "high shelf filter" so "low pass filter" or "LPF" is more common.
• 12 dB per octave - No filter can completely cut off all signal immediately for some frequencies and completely allow it for others. All filters have a "slope" or "quality" which indicates how much the affected frequencies are attenuated. For a low cut filter, higher frequencies are attenuated more. For this filter, the rate of attenuation is 12 dB per octave. An octave is a doubling of frequency. So if the frequency 1000 Hz is affected by this low pass filter, then the frequency of 2000 Hz (one octave higher) will be attenuated to be 12 dB below the level at 1000 Hz. 4000 Hz will be 12 dB lower than 2000 Hz, and so on. Usually a low pass or high pass filter will be created with certain electronics. The smallest amount of electronic components that makes a low or high pass filter creates a slope of 6 dB per octave. That's called a "one-pole" or "first order" filter. IF you double the components, you create a 12 dB per octave low or high cut filter and that is called "two pole" or "second order", and so on. The famous Moog synthesizers are well known for using a four pole LPF with a slope of 24 dB per octave.
• 100 Hz - This is the cutoff frequency*. That means it is the frequency below which the signal is not affected and above which the signal is attenuated at 12 dB per octave. Technically, there is a minor effect at the cutoff frequency, because it is defined as the "3 dB down point", or the frequency where the signal has been attenuated by 3 dB.

So let's look at a specific signal and how this filter would affect it. If we create a white noise source (all frequencies with equal level) at a level of 0 dBu (0.775 Vrms).

Below 100 Hz, all the frequencies will passed through at 0 dBu.

At 100 Hz, the signal will be at -3 dBu.

At 200 Hz, the signal will be at -12 dBu (one octave higher, so 12 dB lower, the -3 is not included here because the "corner is cut off" which creates the -3 at 100 Hz)

At 400 Hz, the signal will be at -24 dBu

At 3,200 Hz, the signal will be at -60 dBu

At 12,800 Hz, the signal will be at -84 dBu

See also: https://en.wikipedia.org/wiki/Low-pass_filter

There are three parameters of this filter that are described in the phrase "100 Hz 12 dB per octave low pass filter". I'll cover them in reverse order.

• Low pass filter - This means the filter does not change lower frequencies ("passes" those frequencies through) and blocks higher frequencies. Sometimes these filters are called "high cut filters", but that can get confused with a "high shelf filter" so "low pass filter" or "LPF" is more common.
• 12 dB per octave - No filter can completely cut off all signal immediately for some frequencies and completely allow it for others. All filters have a "slope" or "quality" which indicates how much the affected frequencies are attenuated. For a low pass filter, higher frequencies are attenuated more. For this filter, the rate of attenuation is 12 dB per octave. An octave is a doubling of frequency. So if the frequency 1000 Hz is affected by this low pass filter, then the frequency of 2000 Hz (one octave higher) will be attenuated to be 12 dB below the level at 1000 Hz. 4000 Hz will be 12 dB lower than 2000 Hz, and so on. Usually a low pass or high pass filter will be created with certain electronics. The smallest amount of electronic components that makes a low or high pass filter creates a slope of 6 dB per octave. That's called a "one-pole" or "first order" filter. IF you double the components, you create a 12 dB per octave low or high cut filter and that is called "two pole" or "second order", and so on. The famous Moog synthesizers are well known for using a four pole LPF with a slope of 24 dB per octave.
• 100 Hz - This is the cutoff frequency*. That means it is the frequency below which the signal is not affected and above which the signal is attenuated at 12 dB per octave. Technically, there is a minor effect at the cutoff frequency, because it is defined as the "3 dB down point", or the frequency where the signal has been attenuated by 3 dB.

So let's look at a specific signal and how this filter would affect it. If we create a white noise source (all frequencies with equal level) at a level of 0 dBu (0.775 Vrms).

Below 100 Hz, all the frequencies will passed through at 0 dBu.

At 100 Hz, the signal will be at -3 dBu.

At 200 Hz, the signal will be at -12 dBu (one octave higher, so 12 dB lower, the -3 is not included here because the "corner is cut off" which creates the -3 at 100 Hz)

At 400 Hz, the signal will be at -24 dBu

At 3,200 Hz, the signal will be at -60 dBu

At 12,800 Hz, the signal will be at -84 dBu

See also: https://en.wikipedia.org/wiki/Low-pass_filter

There are three parameters of this filter that are described in the phrase "100 Hz 12 dB per octave low pass filter". I'll cover them in reverse order.

• Low pass filter - This means the filter does not change lower frequencies ("passes" those frequencies through) and blocks higher frequencies. Sometimes these filters are called "high cut filters", but that can get confused with a "high shelf filter" so "low pass filter" or "LPF" is more common.
• 12 dB per octave - No filter can completely cut off all signal immediately for some frequencies and completely allow it for others. All filters have a "slope" or "quality" which indicates how much the affected frequencies are attenuated. For a low cut filter, higher frequencies are attenuated more. For this filter, the rate of attenuation is 12 dB per octave. An octave is a doubling of frequency. So if the frequency 1000 Hz is affected by this low pass filter, then the frequency of 2000 Hz (one octave higher) will be attenuated to be 12 dB below the level at 1000 Hz. 4000 Hz will be 12 dB lower than 2000 Hz, and so on. Usually a low pass or high pass filter will be created with certain electronics. The smallest amount of electronic components that makes a low or high pass filter creates a slope of 6 dB per octave. That's called a "one-pole" or "first order" filter. IF you double the components, you create a 12 dB per octave low or high cut filter and that is called "two pole" or "second order", and so on. The famous Moog synthesizers are well known for using a four pole LPF with a slope of 24 dB per octave.
• 100 Hz - This is the cutoff frequency*. That means it is the frequency below which the signal is not affected and above which the signal is attenuated at 12 dB per octave. Technically, there is a minor effect at the cutoff frequency, because it is defined as the "3 dB down point", or the frequency where the signal has been attenuated by 3 dB.

So let's look at a specific signal and how this filter would affect it. If we create a white noise source (all frequencies with equal level) at a level of 0 dBu (0.775 Vrms).

Below 100 Hz, all the frequencies will passed through at 0 dBu.

At 100 Hz, the signal will be at -3 dBu.

At 200 Hz, the signal will be at -15 dBu (one octave higher, so 12 dB lower)

At 400 Hz, the signal will be at -27 dBu

At 3,200 Hz, the signal will be at -63 dBu

At 12,800 Hz, the signal will be at -87 dBu

See also: https://en.wikipedia.org/wiki/Low-pass_filter

There are three parameters of this filter that are described in the phrase "100 Hz 12 dB per octave low pass filter". I'll cover them in reverse order.

• Low pass filter - This means the filter does not change lower frequencies ("passes" those frequencies through) and blocks higher frequencies. Sometimes these filters are called "high cut filters", but that can get confused with a "high shelf filter" so "low pass filter" or "LPF" is more common.
• 12 dB per octave - No filter can completely cut off all signal immediately for some frequencies and completely allow it for others. All filters have a "slope" or "quality" which indicates how much the affected frequencies are attenuated. For a low cut filter, higher frequencies are attenuated more. For this filter, the rate of attenuation is 12 dB per octave. An octave is a doubling of frequency. So if the frequency 1000 Hz is affected by this low pass filter, then the frequency of 2000 Hz (one octave higher) will be attenuated to be 12 dB below the level at 1000 Hz. 4000 Hz will be 12 dB lower than 2000 Hz, and so on. Usually a low pass or high pass filter will be created with certain electronics. The smallest amount of electronic components that makes a low or high pass filter creates a slope of 6 dB per octave. That's called a "one-pole" or "first order" filter. IF you double the components, you create a 12 dB per octave low or high cut filter and that is called "two pole" or "second order", and so on. The famous Moog synthesizers are well known for using a four pole LPF with a slope of 24 dB per octave.
• 100 Hz - This is the cutoff frequency*. That means it is the frequency below which the signal is not affected and above which the signal is attenuated at 12 dB per octave. Technically, there is a minor effect at the cutoff frequency, because it is defined as the "3 dB down point", or the frequency where the signal has been attenuated by 3 dB.

So let's look at a specific signal and how this filter would affect it. If we create a white noise source (all frequencies with equal level) at a level of 0 dBu (0.775 Vrms).

Below 100 Hz, all the frequencies will passed through at 0 dBu.

At 100 Hz, the signal will be at -3 dBu.

At 200 Hz, the signal will be at -12 dBu (one octave higher, so 12 dB lower, the -3 is not included here because the "corner is cut off" which creates the -3 at 100 Hz)

At 400 Hz, the signal will be at -24 dBu

At 3,200 Hz, the signal will be at -60 dBu

At 12,800 Hz, the signal will be at -84 dBu

See also: https://en.wikipedia.org/wiki/Low-pass_filter