question about dB's

[Grimfate126]

Today, my physics teacher was talking about sound waves, and dB's. He mathematically showed that if someone was playing an instrument at 70 dB, and another person came in playing at the same loudness, the combined loudness would be 73 dB. This means that a doubling of loudness means a 3 dB increase. However, many sites state that a change in 3 dB is a "barely perceptible", and that 10 dB is required for a doubling in loudness. Whats different?

 

[TLS Guy]

Today, my physics teacher was talking about sound waves, and dB's. He mathematically showed that if someone was playing an instrument at 70 dB, and another person came in playing at the same loudness, the combined loudness would be 73 dB. This means that a doubling of loudness means a 3 dB increase. However, many sites state that a change in 3 dB is a "barely perceptible", and that 10 dB is required for a doubling in loudness. Whats different?

Because of the way we perceive loudness, two saxophones do not sound twice as loud as one. It would take a chorus of ten saxophones to sound twice as loud as one.

 

[annunaki]

Twice the "amplifier power" or "acoustic source power" yields a 3db increase in output. To get a 7db-10db increase (generally thought of as "twice as loud") one needs to increase the amplifier power or acoustic source power by 5x-10x.

 

[Alex2507]

To get a 7db-10db increase (generally thought of as "twice as loud") one needs to increase the amplifier power or acoustic source power by 5x-10x.

I take it that the wiggle room is dependent on maybe the frequency in question, white or pink noise and/or the person being asked?

 

[TLS Guy]

I take it that the wiggle room is dependent on maybe the frequency in question, white or pink noise and/or the person being asked?

The perceptive research on which the db scale is based was done a very long time ago. I think most are agreed that a sound 10db higher in spl. than another having twice the loudness is a little generous. I think the fact that it was made to fit a neat logarithmic scale had a lot to do with how it was set up.

Defining a sound twice a loud as another when 10db higher in intensity, was likely judged close enough and kept things neat and tidy.

In the practical world it works very well.

 

[lsiberian]

Today, my physics teacher was talking about sound waves, and dB's. He mathematically showed that if someone was playing an instrument at 70 dB, and another person came in playing at the same loudness, the combined loudness would be 73 dB. This means that a doubling of loudness means a 3 dB increase. However, many sites state that a change in 3 dB is a "barely perceptible", and that 10 dB is required for a doubling in loudness. Whats different?

That's very interesting isn't it. To understand I suggest you do some reading on how we hear. It can be fascinating.

 

[annunaki]

I take it that the wiggle room is dependent on maybe the frequency in question, white or pink noise and/or the person being asked?

Alex that is correct. Some studies have shown individuals perceiving 6db differences as 2x as loud. It depends upon individual as well as the audible spectrum.

 

[highfigh]

Alex that is correct. Some studies have shown individuals perceiving 6db differences as 2x as loud. It depends upon individual as well as the audible spectrum.

It also depends on the SPL at the start of the test. At high SPL, human hearing tends to compress small increments.

 

[haraldo]

That's very interesting isn't it. To understand I suggest you do some reading on how we hear. It can be fascinating.

Master handbook of acoustics, by F. Alton Everest has a lot of interesting reading on this subject, and many other areas, really recommended reading

 

[highfigh]

Master handbook of acoustics, by F. Alton Everest has a lot of interesting reading on this subject, and many other areas, really recommended reading

I bought a copy of that close to 30 years ago- have you noticed anything in it that doesn't seen right? I did.

I agree though, it's a very good source of information that's less of a college level calculus class.

 

[annunaki]

It also depends on the SPL at the start of the test. At high SPL, human hearing tends to compress small increments.

Good point!