Loudspeakers can produce intense sounds with surprisingly small energy input in spite of their low efficiencies. Calculate the power input needed (in W) to produce a 89.6 dB sound intensity level for a 13.0 cm diameter speaker that has an efficiency of 2.06%. (This value is the sound intensity level right at the speaker.)

Respuesta :

Answer:

[tex]5.87*10^{-4}W[/tex]

Explanation:

Given that:

[tex]\beta = 89,6 dB[/tex]

[tex]D = 13.0 cm[/tex]

[tex]r = \frac{D}{2}\\ = \frac{13.0}{2}\\ = 6.5 cm\\=0.065m[/tex]

Efficiency = 2.06 % = 0.0206

The  intensity level of sound is given by the formula:

[tex]\beta = (10dB) log (\frac{I}{I_o} )[/tex]

[tex]\frac{\beta}{(10dB) } =log (\frac{I}{I_o} )[/tex]

Taking their exponential; we have :

[tex]10^{\frac{\beta}{10dB}}= \frac{I}{I_o}[/tex]

[tex]I = I_o(10^{\frac{\beta}{10dB}})[/tex]

Replacing our values; we have:

[tex]I = (10^{-12}W/m^2)(10^{\frac{89.6}{10dB}})[/tex]

[tex]= 9.12 *10^{-4}W/m^2[/tex]

Power Output;

[tex]P_{out} = IA\\P_{out}=I(\pi r^2)\\P_{out}=(9.12*10^{-4}W/m^2)(3.14)(0.065m)^2\\P_{out}=1.2099048*10^{-5} W[/tex]

The power output that is required to produce a 89.6 dB sound intensity level for a 13.0 cm diameter speaker that has an efficiency of 2.06% is;

[tex]P_{in}= \frac{P_{out}}{0.0206}[/tex]

[tex]P_{in}= \frac{{1.2099048*10^{-5}}}{0.0206}[/tex]

[tex]P_{in}= 5.87*10^{-4}W[/tex]

Therefore, The power output that is required to produce a 89.6 dB sound intensity level for a 13.0 cm diameter speaker that has an efficiency of 2.06% is [tex]5.87*10^{-4}W[/tex]