Clicker question. If a sound has an SIL of 0 db, is any energy transferred? a) Yes b) No c)??

Transcription

1 Clicker question If a sound has an SIL of 0 db, is any energy transferred? a) Yes b) No c)??

2 Phys 1240: Sound and Music LAST TIME: Decibels. TODAY: Decibels. NEXT TIME: Intensity versus distance from source, ears, hearing. READ: 6.1, 6.2 Homework 7 and Reading Question 8 due Thursday. Exam 2 is next Thursday Practice exam posted on course website. No homework next week. Reading question will still be due Thursday.

3 Exam 2 information Multiple-choice exam Exam is open book, emphasis on material in Chapters 3-5 Bring 1-page formula sheet with any notes written on it Bring a calculator Cell phone calculators NOT allowed If your cell phone, ipod, or other device is out (visible) during the exam you get a zero Practice exam is on course website Will do some of these questions as clicker questions next class Review Sessions Tuesday 5-6, Wed 6-7

4 Clicker poll How are Office Hours in the helproom? a) I ve never been to the helproom, but I do need help. b) I ve never been to the helproom, but I don t need help. c) I ve been to the helproom at least once. d) I ve been to the helproom multiple times. e) My schedule doesn t allow me to visit during the scheduled office hours.

5 Review: energy, power, intensity, intrinsic loudness and perceived loudness Energy: Ability to do work transported in the wave Proportional to (Amplitude) 2 Metric Unit is Joule (J) Power: The amount of energy transported per time 1 Joule/second = 1 Watt Intensity: The amount of energy transported per time per area Intrinsic Loudness not Perceived Loudness Perceived Loudness goes with Sound Intensity Level (SIL) in decibels 1 Joule/second/square meter = 1 Watt/m 2

6 Review of Powers of = 10 1 =1E+1 =1E1 100 = 10 2 = 1E+2 = 10E = 10 3 = 1E+3 and so on! 0.1 = 10-1 = 1E = 10-2 = 1E = 10-3 = 1E-3 and so on! What about 1 =??? 1 = 10 0 = 1E0

7 db and intensity (loudness): nothing difficult, it s just a mapping! Here s another example: Presto Vivace Allegretto Andante Adagio Largo A tempo Crescendo Fine Con brio Very fast Lively and fast Rather lively, resonably fast At a walking pace Slow and stately Very slow In time Getting gradually louder The end With brilliance

8 Decibel levels SIL Intensity 0 db I 0 (10-12 W/m 2 ) 10 db 10 I 0 (10-11 W/m 2 ) 20 db 100 I 0 (10-10 W/m 2 ) 30 db 1,000 I 0 (=10 3 I 0 ) (10-9 W/m 2 )

9 SIL Intensity 0 db I 0 (10-12 W/m 2 ) 10 db 10 I 0 (10-11 W/m 2 ) 20 db 100 I 0 (10-10 W/m 2 ) 30 db 1,000 I 0 (=10 3 I 0 ) (10-9 W/m 2 )?? (10-7 W/m 2 ) 100,000 I 0 (=10 5 I 0 )

10 Clicker question 100,000 I 0 (=10 5 I 0 ) (= 10-7 W/m 2 ) corresponds to A) 40 db B) 50 db C) 70 db D) 10 5 db E) None of these/???

11 SIL Intensity 0 db I 0 (10-12 W/m 2 ) 10 db 10 I 0 (10-11 W/m 2 ) 20 db 100 I 0 (10-10 W/m 2 ) 30 db 1,000 I 0 (=10 3 I 0 ) (10-9 W/m 2 ) 50 db 100,000 I 0 (=10 5 I 0 ) (10-7 W/m 2 )

12 SIL Intensity 0 db I 0 (10-12 W/m 2 ) 10 db 10 I 0 (10-11 W/m 2 ) 20 db 100 I 0 (10-10 W/m 2 ) 30 db 1,000 I 0 (10-9 W/m 2 ) 50 db 100,000 I 0 (=10 5 I 0 ) (10-7 W/m 2 ) 100 db?? W/m 2

13 Clicker question 100 db corresponds to what intensity, in W/ m 2? A) W/m 2 B) W/m 2 C) 10-2 W/m 2 D) W/m 2 E) None of these/???

14 Can we make the different levels? SIL Intensity 0 db I 0 (10-12 W/m 2 ) 10 db 10 I 0 (10-11 W/m 2 ) 20 db 100 I 0 (10-10 W/m 2 ) 30 db 1,000 I 0 (10-9 W/m 2 ) 50 db 100,000 I 0 (10-7 W/m 2 ) 100 db I 0 (10-2 W/m 2 )

15 Textbook says: 90 db => Subway train 100 db => Machine shop 110 db => Rock concert 120 db => Jet engine 500 yards away (Painful) 150 db => unbearable

16 These add Decibels as relative SILs These multiply Difference in SIL Ratio of intensities 0 db 1 10 db db db 1, db 100,000 = db 10 10

17 Clicker question There are two instruments, a trumpet and a flute. The trumpet produces a sound with 10x more intensity than that of the flute. The decibel level for the trumpet is compared to the flute. a) 10 db greater b) 10 db less c) 1 db greater d) 1 db less e) Not enough information

18 Clicker question At a concert, the trumpet section is playing 30 db louder than the French horn section. The trumpet section is playing with of the French horn section. a) 3x the intensity b) 10x the intensity c) 30x the intensity d) 1000x the intensity e) x the intensity

19 Clicker question A single flute plays at 60 db. How many flutes (playing together) would be required to raise the SIL to 70 db? A) 2 B) 5 C) 7 D) 10 E) 20

20 Clicker question A trumpet is 20x more intense than a flute. The decibel level of the trumpet is. a) Less than 10 db higher b) 10 db higher c) Between 10 and 20 db higher d) 20 db higher e) More than 20 db higher

21 Diff in SIL Intensity ratio 0 db 1 1 db 2 db 3 db 10 db 10 (etc - see Table 5.1 in text)

22 Diff in SIL Intensity ratio 0 db 1 1 db 1.26 (call it 1.3) 2 db db 2 10 db 10 (etc - see Table 5.1 in text)

23 Adding db corresponds to multiplying intensity +10 db means *10 in intensity +20 db means *100 in intensity Check it out! +20 db is the same as +10 db +10 db Each ADDITION of +10 db means MULTIPLICATION of *10 in the intensity. (*10*10 is the same as *100)

24 Clicker question A trumpet produces a sound 2x more intense than the flute. Compared to the SIL ( decibel level ) of the flute, the decibel level of the trumpet is A) 1.6 db louder B) 2 db louder C) 3 db louder D) 20 db louder E) You can t answer unless I tell you how many db the flute is!