To calibrate a loudspeaker in a test room.

Case:

You have just been asked to work during Mrs. Beeper's pregnancy leave and you will be doing much hearing aid work. However, no one knows how or if the speakers are calibrated. You rent a sound level meter for one day from the Sound Right Brothers. You will only calibrate one, because your friend has offered to do the other one.

Procedure:

Speech:

Check the calibration of the sound level meter using the pistonphone. Position the sound level meter at the calibrated location. Place the sound level meter so that the microphone is at the level of the patient's ear during testing. Select a speaker and deliver speech noise at 70 dB HL.

Warbled Tones:

Repeat as above, except present FM tones (5% frequency deviation) at octave intervals across the frequency range.

For one frequency, record the SPL at the 7 equidistant points in a 15 cm sphere.

Writeup:

1. Compare SPL values with the appropriate references and determine if correction factors are needed for 0 and 45 degrees azimuth. Complete the chart below.

2. Decide whether the test location is adequate for sound-field testing at that frequency when using the FM tone according to the +2dB criteria. If it does not meet the 2 dB criteria, what do you suggest?

Date:_______________________________

Tester:______________________________

Room:_______________________________

Speaker (re: patient):____________________

                            0 Degrees Azimuth

                            250         500     1000          2000       4000    6000   Speech

Obtained

Wanted

Corr.Fac.

                            45 Degrees Azimuth

                            250         500     1000          2000       4000    6000   Speech

Obtained

Wanted

Corr.Fac.

2.) Decide whether the test location is adequate for sound-field testing at the frequency when using the FM tone according to the +2dB criteria. If it does not meet the +2dB criteria, what do you suggest?