Twenty Questions
The Microphone Quiz

This issue's 20 Questions are related to microphones. As always, several of the answers to these questions can be found elsewhere in the September/October 2002 of Live Sound International.

1. The dB is used when measuring mics because:

    A. It's more fun
    B. It's more logarithmic
    C. It's the standard for acoustic pressure measurements in audio
    D. It helps the companies sell more mics

2. 20 micropascals is:

    A. The pressure present at an Atlas III launch
    B. The sound pressure level of the average human's ability to detect a sound
    C. The reference unit for 0dBm
    D. The output pressure from a mic at 1 watt/1 meter

3. What is a Frequency Response Graph?

    A. It illustrates the accuracy with which the mic converts acoustical energy into electrical signals with respect to frequency
    B. It shows the frequencies that the mic will change from acoustical to electrical energy
    C. It's a chart that shows the pick-up patterns
    D. Both A and B

4. What is Sensitivity?

    A. It explains the condition of a used microphone, based on road abuse
    B. It is the amount of dB-SPL that the microphone can handle
    C. It is the measure of the electrical output of a microphone with respect to the acoustic SPL input
    D. It's the pressure in ft-lbs per inch that the mic can take before breaking

5. What happens if you connect a speaker to a mic input on a mixer?

    A. Nothing, as there is no signal
    B. The system goes into unavoidable violent feedback due to oscillations
    C. The speaker works like a big microphone
    D. Your co-workers laugh like hell because they think you're an idiot

6. Proximity Effect:

    A. Occurs when two transducers get too close to each other
    B. Is an increase in LF response when a cardioid mic is close to an acoustic source
    C. Happens when measuring a speaker with an RTA
    D. Happens when a mic gets too close to a speaker

7. When a mic that is 3 inches in front of a singer is moved to 6 inches, the level will:

    A. Drop 3 dB
    B. Drop 6 dB
    C. Drop 9 dB
    D. Stay the same

8. The tightest cardioid pick-up pattern is:

    A. Sub-cardioid
    B. Cardioid
    C. Super-cardioid
    D. Hyper-cardioid

9. An omni mic placed a few millimeters away from a reflective surface creates an effect identical to a:

    A. Rifle or shotgun mic
    B. Lavaliere mic
    C. Parabolic mic
    D. PZM or Boundary mic

10. The FCC limits the transmission power of wireless mics to:

    A. 1mW
    B. 5mW
    C. 10mW
    D. 50mW

11. Shure introduced the 3B and 10B Carbon microphones in:

    A. 1916
    B. 1926
    C. 1936
    D. 1946

12. The Sennheiser MD421 was introduced in:

    A. 1955
    B. 1960
    C. 1965
    D. 1970

13. What stereo micing technique uses a coincident pair of two bi-directional microphones in the same point, angled at 90° to each other?

    A. M-S
    B. ORTF
    C. Decca Tree
    D. Blumlein stereo

14. What stereo micing technique uses two cardioid mics with the capsules spaced 17cm apart, with the two mics at a 110° angle creating the stereo image?

    A. M-S
    B. ORTF
    C. Decca Tree
    D. Blumlein stereo

15. What stereo micing technique uses a cardioid microphone capsule as center channel and a bi-directional figure-eight-mic at the same point, angled at 90°, which is then brought in on faders, out-of-phase to create the stereo image?

    A. M-S
    B. ORTF
    C. Decca Tree
    D. Blumlein stereo

16. A PZM receives direct and reflected sound simultaneously.

    True or False?

17. The Crown PCC is an omnidirectional microphone.

    True or False?

18. If wired according to the AES standard, pin 2 of a microphone's XLR connector will:

    A. Always be ground
    B. Always be “hot” or positive
    C. Always be “low” or negative
    D. Be the connection for +52VDC

19. An Electret microphone:

    A. Is never used in pro audio
    B. Is a form of ribbon microphone
    C. Is a crystal microphone with special permanent polarization
    D. Requires a power supply

20. Which microphone naturally has a figure eight or bi-directional pick-up pattern?

    A. Condenser
    B. Ribbon
    C. Carbon
    D. Dynamic

Twenty Answers

1. C

2. B, 20 micropascals is 0dB-SPL, which is the hearing threshold of the average human at roughly 3kHz. At other frequencies, the hearing threshold is affected by the loudness contour making it much higher at very low or very high frequencies.

3. D

4. C, The sensitivity states what voltage a microphone will produce with a certain sound pressure level input. A microphone with high sensitivity will give a high voltage output and will therefore not need as much amplification (gain) as a model with lower sensitivity.

5. C and D

6. B

7. B, It drops 6 dB and so does the gain-before-feedback capability.

8. D

9. D, Using an omni against the floor or taped to a wall with the diaphragm within a 1/8-inch off the surface puts it in the pressure zone for most of the audio bandwidth.

10. D

11. C

12. B

13. D

14. B, ORTF stands for Office de Radiodiffusion Television Francais.

15. A

16. True

17. False, the PCC series are half-cardioids and half-super-cardioids.

18. B, Positive pressure on the mic's diaphragm will produce a positive voltage on pin 2.

19. D, It needs either phantom power from the mixer it's plugged into or a battery.

20. B

September/October 2002 Live Sound International

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