Richard Jackett

Waka Kotahi NZ Transport Agency · Environment and Sustainability

Refracto-vibrometry is a relatively new measurement technique that is sensitive to variations in the optical refractive index of a medium caused by changes in acoustic pressure within that medium (the acousto-optic effect). It has so far been employed primarily as a qualitative visualization tool for airborne sound propagation because determining s...

A study into the road traffic noise emission of heavy vehicles, with a focus on the tyre/road interaction. The purpose was to inform future effort on road surface noise research in New Zealand. The CNOSSOS-EU model and traffic telemetry data were used to estimate the contribution of truck rolling noise to the overall road traffic noise emission, an...

Pressure reciprocity calibration of microphones provides the basis for primary measurement standards for sound pressure in air. At low frequencies, reciprocity calibration requires that a heat conduction correction be employed to account for energy transfer to and from the bounding surfaces of the close-coupled microphone arrangement. The standard...

A novel methodology for deriving road surface noise corrections has been devised and implemented. It used a large CPX noise survey of the network to accurately classify the performance of different surface types. CPX levels were correlated against wayside single vehicle pass-by levels and a CPX-wayside transfer function derived. A requirement to re...

Longitudinal variability in tyre/road noise is often associated with low-noise porous asphalt surfaces, with CPX testing results for individual 20-metre road segments commonly varying by up to 6 dB along new projects in New Zealand. In November 2018, following on from previous trials investigating the effects of air voids and stone size, three EPA7...

Since 2017, several porous asphalt trials have been built in New Zealand in order to investigate the effects of air voids, stone size and layer thickness on tyre/road noise. These trials have shown that all three variables play an important role in noise from porous asphalt surfaces. The trial results have led to a 40 mm thick EPA7 surface (porous...

An overview of NZ road surfacing aggregates, in the context of tyre/road noise emissions, focusing on intrinsic properties of the aggregates rather than production properties such as chip size or quality of quarry operation. Aggregate properties of interest to noise generation are identified. Engineering properties and tests of NZ aggregates are di...

A provisional study to establish the NZTA CPX trailer's capability for measurement of chipseal through paired CPX and wayside noise measurements. A total 700 km of state highway were surveyed using P1, H1, and 'typical' car tyres and 6 SPB measurements made. The inherent repeatability of CPX measurement was established; variability within surface s...

The aim of this study is to use wayside (SPB) measurements and alternate tyres to validate the CPX rankings of specific epoxy OGPA test surfaces in Christchurch, New Zealand. The study was also able to provide a quantitative relationship between CPX and SPB; compare old and new tyres of the same make/model; compare the SRTT (P1) tyre to a typical p...

Post-crash care of victims is considered by the World Health Organisation to be the fifth pillar of the safe system approach to road safety. Timeliness and quality of transport of crash victims from the crash site to hospital door is crucial to medical outcomes. It is important that road controlling authorities (RCAs) and Road Policing work togethe...

Research was commissioned to investigate the long-term acoustic performance of New Zealand standard porous asphalt made to TNZ P/11 Specification for open graded porous asphalt (OGPA). The research findings should be considered applicable only to New Zealand OGPA laid in high-speed environments (speed limits of 80 to 100 km/h). A method for acousti...

Wind-borne noise occurs as a result of high frequency fluctuations either in the pressure or the velocity field. The main mechanisms behind wind-induced noise problems in the context of urban flow are: Aeolian tones, typically generated by high frequency vortex shedding in the wake of strong flow separation off a sharp edged object (often an archit...

The primary standard for sound pressure is defined through the reciprocity calibration procedure specified in IEC 61094-2, placing a unique reliance on the accuracy of the published standard. The technique involves forming configurations of pairs of microphones together with an air-filled coupler. Over most of the frequency range, adiabatic conditi...

Refracto-vibrometry is a relatively new measurement technique that is sensitive to variations in the optical refractive index of a medium caused by changes in acoustic pressure within that medium (the acousto-optic effect). It has recently found applications in underwater acoustics but NPL have successfully applied this technique to sound in air us...

A practical example of a statistical method is presented for stability assessment of noise monitoring networks based on the comparison between statistical levels measured by multiple measurement stations in a network. The method makes use of an adaptation of the Chow Test and relies on the comparison of sum of squared residuals from linear regressi...

The calibration of laboratory standard microphones by the pressure reciprocity method, as specified in IEC 61094-2, is used throughout the world as the basis for primary measurement standards for sound pressure. While the method has long been used to determine the magnitude of the pressure sensitivity of the microphone, the phase sensitivity has un...

Pressure-field calibration and free-field calibration of laboratory standard microphones is well established, but diffuse-field calibration still has no accepted or standardised methodology. Yet there is growing demand for diffuse-field calibrated microphones in areas such as building compliance testing and indoor noise measurement. Two approaches...

Ear simulators are important measurement devices for characterizing the performance and acoustic output of earphones and other transducers designed to be coupled to human ears. For best practice in the use of these devices it is important that the acoustic transfer impedance is periodically tested against published specification. This practice has...

Many road designations have conditions with respect to noise that require that when the road is completed, measurements will be undertaken to prove that the performance standards of those conditions have been fulfilled. However all measurements are subject to variability, and the designation conditions do not address either the expected nature of t...

The calibration of measurement microphones has traditionally focused on determining the sensitivity magnitude. However most primary and secondary calibration techniques can be readily adapted to also yield the phase response. Sound intensity measurements have long required the relative phase response of two microphones to be known with a high preci...