Extech 407750 Sound Level Meter with PC Interface.

Sound Level Meter with PC Interface and Background Noise Filter
Sound Level Meter meets ANSI and IEC 651 Type 2 standards. Ideal for noise surveys in the workplace, installing fire alarms and speaker systems, and enforcing noise ordinances. Measures from 30 to 130 dB in two ranges and has an accuracy of ±1.5 dB. The built-in background noise absorber for machine noise measurements filters ambient noise for more accurate readings. Data hold and Min/Max functions. Backlit display allows use in dimly lit areas. The meter also has an RS232 interface for capturing data directly to your PC using optional Windows compatible software (407752). 

What is a Sound Level Meter?
Sound level meters are instruments designed to respond to noise much like the human ear. The measurements taken by sound level meters are compared to known standards to determine if the noise level could have a detrimental effect on human hearing.

Types of Sound Level Meters

• Type 3 — Low cost models for basic sound checks.
• Type 2 — Models that meet OSHA and other ordinance testing requirements.
• Type 1 — Precision for lab testing (Extech doesn't have one).
• Dosimeters — Measure work noise exposure according to OSHA.
• Analyzer — analyzes noise in narrow bands.