G.R.A.S. 40HH, 12HF Instruction Manual

Instruction Manual

Single-channel Low-noise Measuring
System consisting of:
½-inch Low-noise Level Microphone
System Type 40HH and
Power Module Type 12HF

40HH

12HF

G.R.A.S.

Sound & Vibration

Skovlytoften 33, 2840 Holte, Denmark Tel. [phone] Fax [phone]

Single-channel Low-noise Measuring System

consisting of:

• ½″ Low-noise Level Microphone System Type 40HH

• Power Module Type 12HF

Revision 17 September 2017

CONTENTS

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.1 Microphone Type 40AH .............................................3

1.2 Preamplier Type 26HH .............................................3

2 Power Module Type 12HF. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.1 Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.2 Rear Panel .......................................................8

2.3 Battery Pack ......................................................9

3 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.1 Based on System Sensitivity .........................................10

3.2 Level Calibratinon using a Pistonphone ................................10

3.3 Frequency Response Calibratoin .....................................11

4 Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

5 Specications ..................................................12

5.1 ½″ Low-noise Microphone System Type 40HH. . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5.2 Single-channel Power module Type 12HF (separate order) ................. 12

5.3 Common . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6 What to Order ..................................................14

G.R.A.S. SOUND & VIBRATION

1 Introduction

Fig. 1.1 shows a ½″ Low-noise Level Microphone System Type 40HH which comprises:

• ½″ Microphone Type 40AH.

• ½″ Preamplier Type 26HH with two built-in compensation lters and an overload-warning

LED.

To complete the system, a special single or 10-channel power module is required and is avail-

able from G.R.A.S., i.e.

• Type 12HF for single-channel measurements, see Fig. 1.2 (left)

or

• Type 12HM for multi-channel (1 to 10) measurements, see Fig. 1.2 (right).

The chosen power module provides all necessary voltages for powering the preamplier(s) as
well as polarizing the microphone(s).

Fig. 1.3 shows a Single-channel Low-noise Measuring system (as described in this document)
and consists of:

• ½″ Low-noise Level Microphone System Type 40HH.

• Power Module Type 12HF.

Note: the power module must be ordered separately, and the tripod and tripod adapter are

optional extras.

Single-channel Low-noise Measuring System consisting of: Type 40HH and Type 12HF - Page 4

Overload-warning LED indicates when the measured

sound pressure level overloads the system’s electronics

Fig. 1.1 ½″ Low-noise Measurement Microphone System Type 40HH

1.1 Microphone Type 40AH

The Type 40AH is a special high-sensitive ½″ microphone. It is externally polarized with a spe­cially reduced inherent noise oor in order to achieve a high dynamic range and wide frequency

range.

1.2 Preamplier Type 26HH

The body of the Preamplier has an overload-warning LED, (Fig. 1.1), which is repeated on the
front panel of the chosen power module (see Fig. 2.1).

The signal of the microphone is amplied by 20 dB in the Preamplier Type 26HH.

The two compensation lters give the system two parallel outputs which correspond to:

a) linear pressure-frequency response

b) linear free-eld frequency response at an angle of 0 ° incidence.

The choice of which frequency response to use is made via a two-position switch marked
Pressure / Free Field on the front panel of the chosen power module (see Fig. 2.1).

Fig. 1.4 shows the responses of the two compensation lters as well as the free-eld response
for 0 ° incidence. Note: free-eld corrections are added to the lowest curve.

Fig. 1.5 shows what these free-eld corrections are for various angles of incidence.

Fig. 1.6 shows, for a complete low-noise measuring system, a typical noise oor in ⅓-octave
bands for both the linear and A-weighted cases.

G.R.A.S. SOUND & VIBRATION

Single-channel Low-noise Measuring System consisting of: Type 40HH and Type 12HF - Page 5

Fig. 1.2 Power modules available from G.R.A.S. for Type 40HH,
Left: Single-channel Power Module Type 12HF
Right: 10-Channel Module Type 12HM

½″ Low-noise Level Microphone

System Type 40HH

Tripod
Adapter
RA0093

Tripod

AL0006

Single or 10-chan­nel power module
(here single chan­nel Power Module
Type 12HF)

Fig. 1.3 A Single-channel Low-noise Measuring System as described in this document;
shown here with Tripod and Tripod Adapter (both available from G.R.A.S.)

G.R.A.S. SOUND & VIBRATION