Cirrus Research · Optimus+ · Handheld sound level meter
Optimus+ Environmental Sound Level Meter
CurrentHandheld Class 1 or Class 2 data-logging sound level meter for environmental noise, measuring all weightings simultaneously in a single 20 to 140 dB range with Ln statistics, triggered audio recording and Lden control. Versions add 1:1 octave bands or 1:1 and 1:3 octave bands with tonal noise detection. It is the measuring unit of the Cirrus Outdoor Environmental Noise Kit.
Specifications verified on .
- Type
- Handheld sound level meter
- Class
- Class 1
- Channels
- 1
- Octave bands
- 1/1 and 1/3
- Connectivity
- USB type B, Bluetooth Low Energy, AC/DC output, GPS (GPS model)
- Weight
- 300 g
- Battery life
- 12 h
Specifications
As published by Cirrus Research. Fields the manufacturer does not publish are omitted rather than estimated.
| Specification | Value |
|---|---|
| IEC 61672-1 class | Class 1 |
| Standards | IEC 61672-1:2013 class 1 or class 2, IEC 61260 and ANSI S1.11-2004 (1:1 and 1:3 octave filters), IEC 60651, IEC 60804, ANSI S1.4, ANSI S1.43, DIN 45657 |
| Pattern approvals | PTB (class 1), LNE (class 1) |
| Recommended calibration interval | 12 months |
| Specification | Value |
|---|---|
| Channels | 1 |
| Measurement range | 20 to 140 dB, single range |
| Frequency range | 6.3 Hz to 20 kHz (1:3 octave bands measured; 12.5 Hz to 20 kHz displayed) |
| Frequency weightings | A, C, Z |
| Time weightings | F, S, I |
| Simultaneous weightings | Yes |
| Parameters | LXeq, LXYmax, LXYmin, LCpeak, LZpeak, LXE, Ln statistics, Lden, Leq LF (20 to 200 Hz), tonal noise detection (C models) |
| Specification | Value |
|---|---|
| Octave bands | 1/1 and 1/3 |
| Audio recording | Yes |
| Specification | Value |
|---|---|
| Shortest logging interval | 10 ms |
| Memory | 8 GB standard; 32 GB factory option |
| Specification | Value |
|---|---|
| Microphone | class 1: MK:224 1/2" pre-polarised; class 2: MK:216 pre-polarised |
| Detachable preamplifier | Yes |
| Outdoor microphone kit | Outdoor Environmental Noise Kit (CK:67x/68x) with MK:172 outdoor microphone |
| Display | high-resolution OLED with ambient light sensor and illuminated keypad |
| Battery | 4 x AA alkaline or lithium |
| Battery life | 12 h |
| External power | 5 to 15 V DC via ZL:171 cable |
| Weight | 300 g |
| Dimensions (mm) | 283 x 65 x 30 |
| Operating temperature (°C) | -10 to 50 |
| Specification | Value |
|---|---|
| Connectivity | USB type B, Bluetooth Low Energy, AC/DC output, GPS (GPS model) |
| Remote control | MyCirrus mobile apps via Bluetooth; remote access via Outdoor Kit modem |
| Software | NoiseTools, MyCirrus app |
Variants
| Variant | Difference |
|---|---|
| CR:171A / CR:172A | Class 1 / class 2 data-logging meter with Ln statistics |
| Octave band model | Adds real-time 1:1 octave bands (31.5 Hz to 16 kHz) |
| CR:171C / CR:172C | Class 1 / class 2 with 1:1 and 1:3 octave bands, tonal noise detection and 14 additional Ln values with independent weightings |
| Optimus+ GPS | Adds GPS location data to each measurement |
Where this data comes from
| Kind | Document | Accessed |
|---|---|---|
| Product page | Optimus+ Environmental Sound Level Meter | |
| Datasheet | Optimus+ Environmental datasheet (English, 2026) | |
| Manual | Optimus user manual (English) |
Verified on . Only the manufacturer’s own published material is used; distributor pages are not sources.
Spec out of date? Tell us (reference cirrus-optimus-plus-environmental).
Verified owner reviews
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Known issues and firmware notes
Hardware and firmware problems reported by owners, with the firmware version concerned and any manufacturer response.
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Feature requests
Functions owners would like to see in a firmware update or a successor model.
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Read next
- How to choose a sound level meter · Class 1 vs class 2, integrating vs non-integrating, parameters by application, options and licences, calibration.
- Class 1 vs class 2 sound level meters · IEC 61672-1 tolerances, what the classes do and do not say, and where each is typically required.
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