<prompt> 40 db compared to 20 db is -Double10 times100 times1000 times  <response>: SPL Sound pressure levelIf a sound has an SPL of 1000 i.e 103 times, the reference of sound, it is expressed as20 × log 1000 20 × 3 60 dB as log 1000 3Now in the Q sound is 20 dB, that means to get 20 as the answer, 20 has to be multiplied by 1, i.e the SPL of this sound is 10 becauselog 10 is 1.Now it is being compared with 40 dBTo get 40 dB as the answer.20 has to be multiplied by 2 which means log of x 2, therefore x 100So it means this sound should have SPL 100Now see 20 dB SPL 1040 dB SPL 100i.e. 40 dB is 10 times of 20 dB 