Noise Measurement – Acoustic Box Experiment (30%) WHS Note: The Dynamics and Mechanics of Solids Laboratory is considered a low risk environment. However, students are reminded to wear closed footwear (no sandals or thongs) and to strictly follow the supervisor’s instructions. This experiment will be conducted on the ‘Acoustic Box’, which is located in the Dynamics and Mechanics of Solids Laboratory, CB11.B4.105. The roll with be taken and you are instructed to turn up at your allotted session time listed below. Session A: 09:00-09:45 hr Tuesday 11 April 2017 Session B: 10:00-10:45 hr Tuesday 11 April 2017 Session C: 11:00-11:45 hr Tuesday 11 April 2017 Laboratory space is limited - please ensure that you attend at your allocated session time. The Acoustic Box is a piece of apparatus that was designed to be configured in a variety of different acoustical attenuation and absorption modes. It has 7 configurations (fully open with the speaker exposed, box with front wall removed, box with front wall removed and fitted with an internal absorber, box with front wall fitted with an opening, fully closed, the same as Configuration 4 but with an attenuation pathway and a folded attenuation pathway added to the opening) as shown in Figure 1. Configuration 1 Configuration 2 Configuration 3 Configuration 4 Configuration 5 Configuration 6 Configuration 7 Figure 1: Seven configurations of the Acoustics Box. The purpose of this experiment is for the student to use this apparatus to demonstrate by way of measurement and documentation a number of fundament acoustical properties including: • Attenuation; • Absorption; • Effect of small openings; and • Any other acoustical properties that you may observe during the experiment. Because of limited session time, the basic requirements for Session A is doing measurements for Configurations 1-3, for Session B is doing measurements for Configurations 3-5, and for Session C is doing measurements for Configurations 5-7. If the students have spare time in their session, they are welcome to do measurements for the configurations in other sessions. Each student needs write an INDIVIDUAL REPORT in standard laboratory format with a maximum of 8 pages. For example, the report should have sections of Aim, Method, Results, Discussion, Conclusion, and sketches of the measurement arrangement and setup, etc. A separate sub-section for each major deliverable (i.e., attenuation, absorption, and effect of small openings) could be included within the report, and each sub-section can include discussion on the relevant underlying acoustical theory and how the data compares to the theory. Due: 5:00 pm, 27 April 2017 – This Assignment shall be submitted ELECTRONICALLY via UTS online (https://online.uts.edu.au/). No assignment will be accepted after the deadline (i.e., 0 mark). Xiaojun Qiu 10 April 2017 Noise Measurement Procedures and Datasheet Student Name: Student No.: Date: Instrumentation Name and Serial No.: (1) (2) (3) (4) (5) Calibration Check: SLM 1: dB, SLM 2: dB before measurements; SLM 1: dB, SLM 2: dB after measurements Measurement Procedures 1. Measure and record the key geometry dimensions of each configuration in the session you are assigned. 2. Measure the distance between the Sound Level Meters (SLMs) and the sound source. 3. Get familiar with the operation of the sound source and make sure that the signal generator products 5.0 Vpp white noise. 4. Get familiar with the SLMs, check the setup of the SLMs, and carry out the calibration check with a calibrator. 5. Measure and record the octave band linear sound pressure levels (SPLs) from 16 Hz to 16 kHz, the linear total SPL (Lz), and the A-weighted total SPL (LA) with SLM 1 and the linear total SPL (Lz) with SLM 2 of the background noise. 6. Measure and record the octave band linear SPLs from 16 Hz to 16 kHz, the linear total SPL (Lz), and the A-weighted total SPL (LA) with SLM 1 and the linear total SPL (Lz) with SLM 2 under different configurations with the sound source on. 7. Carry out the calibration check for the SLMs with a calibrator after the measurements. Step Name Activity Comments 1 Calibration Check Use a sound calibrator to check the SLMs 2 Background Noise Measure and record the un-weighted (linear) SPLs in octave bands (16-16k Hz), the overall linear SPL and A weighted SPL THIS MUST BE DONE FOR EVERY SESSION 3 Configuration 1 The same as that of Step 2 fully open with the speaker exposed 4 Configuration 2 The same as that of Step 2 box with front wall removed 5 Configuration 3 The same as that of Step 2 box with front wall removed and fitted with an internal absorber 6 Configuration 4 The same as that of Step 2 box with front wall fitted with an opening 7 Configuration5 The same as that of Step 2 fully closed 8 Configuration 6 The same as that of Step 2 same as Configuration 4 but with an attenuation pathway added to the opening 9 Configuration 7 The same as that of Step 2 same as Configuration 4 but with a folded attenuation pathway added to the opening 10 Calibration Check Use a sound calibrator to check SLMs Measurement Datasheet Table 1 – The Measured Sound Pressure Level (dB) Freq. (Hz) Configuration Sound Level Meter 1 (SLM 1) SLM 2 16 31.5 63 125 250 500 1 k 2 k 4 k 8 k 16 k Linear Total SPL A-weighted Total SPL Linear Total SPL Background Noise Configuration 1 Configuration 2 Configuration 3 Configuration 4 Configuration 5 Configuration 6 Configuration 7 Other issues happened in the measurements: