Question

3. 1324	Dr. Lyon plays a tuba such that the sound level is 48 dB at a distance of 5 m from himself. Dr. Ryder plays another tuba such that sound level is 57 dB at a distance of 5 m from him.

Part	Description	Answer	Save	Status
A.	What is the sound level at 5 m when both Dr. Lyon and Dr. Ryder play their tubas together? (±0.2 dB)		7.86 pts.110% 2% try penalty Bonus hint Hints: 1,0	# tries: 0
B.	Dr. Stewart now joins Drs. Lyon and Ryder in playing tubas. At what sound level does Dr. Stewart need to play his tuba so that the combined sound level at 5 m is 60 dB? (±0.2 dB)		7.86 pts.110% 2% try penalty Bonus hint Hints: 0,0	# tries: 0
C.	At what distance is the sound level from the three distinguished tuba players 37 dB? (include units with answer)	Format Check	7.86 pts.110% 2% try penalty Bonus hint Hints: 0,0	# tries: 0

0

Answer 1

given

L_A = 48 dB

L_B = 57 dB

a )

L = 10 log₁₀ ( 10^LA/10 + 10^LB/10 )

= 10 log₁₀ ( 10^48/10 + 10^57/10 )

= 10 log₁₀ ( 10^4.8 + 10^5.7 )  

L = 57.514 dB

b )

60 = 10 log₁₀ ( 10^48/10 + 10^57/10 + 10^LC/10 )  

6 = log₁₀ ( 10^48/10 + 10^57/10 + 10^LC/10 )  

6 = log₁₀ ( 10^4.8 + 10^5.7 + 10^LC/10 )  

L_C = 10 log₁₀ ( 10⁶ - ( 10^4.8 + 10^5.7 ) )

L_C = 56.392 dB

c )

L₁ = 60 dB

L₂ = 37 dB

r₁ = 4 m

r₂ = ?

r₁ = r₂ / 10 ^{( L1} - ^{L2 /20 )}

r₂ = r₁ x 10^60-37/20

= 4 x 10^23/20

r₂ = 56.5 m