Sound Power Response vs. Frequency Response

JasonI

New Member
Dec 3, 2010
67
0
0
#1
Dr. Olive, I have many questions that hopefully you can help shed light on.

1. How does sound power response relate to frequency response? Dr. Olive, you're the only person I've seen use the phrase with any regularity and it's inserted doubt into my understanding of frequency response, particularly regarding measurement methods.

2. Is sound power response a different type of measurement than a frequency response measurement? It's my understanding that frequency response measurements are taken with enough power to produce 'reference levels' with sine sweeps, though with no real industry standard. Am I on the right track?

3. If different, how does a frequency response measurement differ from one that finds sound power response?
 

tonmeister2008

WBF Technical Expert
Jun 20, 2010
210
0
0
Westlake Village,CA
#3
Dr. Olive, I have many questions that hopefully you can help shed light on.

1. How does sound power response relate to frequency response? Dr. Olive, you're the only person I've seen use the phrase with any regularity and it's inserted doubt into my understanding of frequency response, particularly regarding measurement methods.

2. Is sound power response a different type of measurement than a frequency response measurement? It's my understanding that frequency response measurements are taken with enough power to produce 'reference levels' with sine sweeps, though with no real industry standard. Am I on the right track?

3. If different, how does a frequency response measurement differ from one that finds sound power response?
1. The frequency response is a curve plotting the amplitude response (y-axis) as a function of frequency (x-axis). When talking about the frequency response of a loudspeaker, you must always reference the location of the microphone with respect to the loudspeaker since the frequency response will vary with location. Typically, manufacturers show the on-axis response where the microphone is placed on the reference axis of the loudspeaker. We also show a listening window frequency response that represents a spatial average of several microphone positions around the reference axis of the loudspeaker. We also show the spatial average of the first reflections where the microphone is placed at several angles where sound radiated ends up at the listening position from the first floor/ceiling/side/front/rear walls -- based on a survey of loudspeaker setups in different homes.

The sound power response is the frequency response of the total radiated sound produced from the loudspeaker at different frequencies. This can be measured by measuring the loudspeaker in a reverberation chamber or calculated by measuring the loudspeaker in an anechoic chamber at many angles around a sphere. We do a total of 70 different measurements in the vertical and horizontal orbits (every 10 degrees) and then calculate the sound power response from those measurements.

Your impression of the sound quality of a loudspeaker in a room is based on a combination of the direct, early and late reflected sounds produced by the loudspeakerTherefore, to accurately predict the loudspeakers' sound quality you need a lot of anechoic frequency response measurements that characterize the direct sound (on-axis//listening window frequency response curve, the early reflected sound(first reflection frequency response curve), and the late reflected sound (sound power response). We've shown that with this data, you can accurately predict the measured in-room response in a typical room between 200-300 Hz and 10 kHz. Below 300 Hz the room dominates what you hear (room resonances, solid boundary gain). Above 10 kHz or so, the absorption from air and room treatment will influence the late arrivals.
 

AndreaPM

New Member
Sep 23, 2016
1
0
0
#4
But how Boxsim does know the driver behaviour at 15/30/45 degrees...

1. The frequency response is a curve plotting the amplitude response (y-axis) as a function of frequency (x-axis). When talking about the frequency response of a loudspeaker, you must always reference the location of the microphone with respect to the loudspeaker since the frequency response will vary with location. Typically, manufacturers show the on-axis response where the microphone is placed on the reference axis of the loudspeaker. We also show a listening window frequency response that represents a spatial average of several microphone positions around the reference axis of the loudspeaker. We also show the spatial average of the first reflections where the microphone is placed at several angles where sound radiated ends up at the listening position from the first floor/ceiling/side/front/rear walls -- based on a survey of loudspeaker setups in different homes.

The sound power response is the frequency response of the total radiated sound produced from the loudspeaker at different frequencies. This can be measured by measuring the loudspeaker in a reverberation chamber or calculated by measuring the loudspeaker in an anechoic chamber at many angles around a sphere. We do a total of 70 different measurements in the vertical and horizontal orbits (every 10 degrees) and then calculate the sound power response from those measurements.

Your impression of the sound quality of a loudspeaker in a room is based on a combination of the direct, early and late reflected sounds produced by the loudspeakerTherefore, to accurately predict the loudspeakers' sound quality you need a lot of anechoic frequency response measurements that characterize the direct sound (on-axis//listening window frequency response curve, the early reflected sound(first reflection frequency response curve), and the late reflected sound (sound power response). We've shown that with this data, you can accurately predict the measured in-room response in a typical room between 200-300 Hz and 10 kHz. Below 300 Hz the room dominates what you hear (room resonances, solid boundary gain). Above 10 kHz or so, the absorption from air and room treatment will influence the late arrivals.
Dear Dr. Olive,
But how does Boxsim know the driver response behaviour at 15/30/45 degrees if I give only the on-axis response of the drivers mounted on my box? Boxsim just "guess" considering the dimensions and shapes of the cone/dome? Every driver have different off axis responses that don't depend just on the cone/dome shape and size.
There are no possibilities to import my horizontal and vertical measured off axis responses in Boxsim? Ok I will not take so many measures as may be needed but sure I can take responses at 15,30,45 and 90 and then Boxsim could use them to simulate a more realistic sound power response.

Thank you for your kind attention!
My kindest regards
Andrea P. Merlo
 
Mar 1, 2018
1
0
0
#5
Hello Dr. Olive,

I had a question on Sound Power and Frequency.

If a source of power produced noise at a frequency, say 100Hz, and I measured the pressure and velocity of the air particles at a distance, say 3 ft away from the source and then I repeated the same test (everything being identical) except the source now produces a noise at 5000 Hz, what would be the difference in pressure and velocities?

Thanks!
 

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