$(50\%)$ A sound$-$producing engine in a large factory is separated from an adjacent school by two

walls built for noise isolation. The surface area of the walls is $100m^2.$ The engine is mounted on

concrete at a distance of $40$ m to the first of these walls. The relative humidity in the factory is

$50\%$ and the temperature is $20C.$ There is a scattered area near the wall in the factory. The

factory has a directivity coefficient $(Q)$ of $2$ and a room constant of $20m^2$ Sabine for all

frequencies. The sound power levels produced by the engine are given below

The first of the walls separating the school and the factory is $10$ cm thick, with a surface density

of $15\frac{\frac{kg}{m^2}}{c}m$ and a plateau height of $20$ dB $,$ and the second $($with $50$ cm spacing from the first

wall$)5$ cm thick, with a surface density of $12\frac{\frac{kg}{m^2}}{c}m$ and a plateau height of $20$ dB $.$ Room

constants in the school were calculated and found as follows

Calculate the total sound pressure level in terms of phon that a student $30$ m away from the wall in the

school $($Assume that temperature in the school is $20C$ and relative humidity is $15\%)$ will hear.

$($B$$y$$k bir fabrikada ses $$reten bir motor, biti$$ikteki bir okuldan g$$r$$lt$$ yal$$t$$m$$ i$$in in$$aa

edilmi$$ iki duvarla ayr$$lm$$t$$r$.$ Duvarlar$$n y$$zey alanlan $100m^2$ 'dir. Motor bu duvarlardan ilkine

$40$ m mesafeye beton $$zerine monte edilmi$$tir$.$ Fabrika i$$inde ba$$l nem $\%50$ ve s$$cakl$$k $20$

$$ 'dur. Fabrikada duvar yak$$n$$nda da$$n$$k alan olu$$maktad$$r$.$ Fabrikada y$$nelme katsay$$s$2$ ve

b$$t$$n frekanslar i$$in oda sabiti $20m^2$ Sabine'dir. Motorun $$retti$$i ses g$$c$$ seviyeleri a$$a$$da

verilmi$$tir$.$

Okul ile fabrikay$$ ay$$ran duvarlardan birincisi $10$ cm kal$$nlkta olup, y$$zey yo$$unlugu $15\frac{\frac{kg}{m^2}}{c}m$ ve plato

yuksekli$$i $20$ dB $,$ ikincisi ise $($birinci duvardan $50$ cm aral$$kli$)5$ cm kal$$nlikta olup, y$$zey yogunlu$$u $12(\frac{kg}{m^2})cm$

ve plato yuksekli$$i $20$ dB olan malzemeden in$$aa edilmi$$tir$.$ Okuldaki oda sabitleri hesaplanm$$ ve a$$a$$daki gibi

bulunmu$$ur$.$

Okul i$$inde duvardan $30$ m uzaktaki bir $$rencinin $($okul i$$indeki s$$cakl$$k $20C$ ve ba$$l nem

$\%15$ kabul edilebilir$)$ i$$itece$$i toplam ses bas$$nc$$ seviyesini phon cinsinden hesaplay$$n$$z$.)$

Some formulae:

$TL=20lo{g}_{10}of-47,A_{wn}=7\mathrm{.}4{10}^{-3}{f}^{\text{'}}r,S_t=S_n+K({\displaystyle \underset{t=1}{\overset{n}{}}}{S}_t-S_n)$

$SBS=SGS+10lo{g}_x(\frac{9}{4r^2}),S=2^{\frac{I+m^{-sf}}{10}}$