Quiet Window Research Articles

A design methodology for acoustic resonance-free, high-frequency, dimmable electronic ballast for high-pressure sodium-vapour lamps

This paper presents a methodology to design acoustic resonance-free, high-frequency, dimmable electronic ballasts for high-pressure sodium vapour (HPSV) lamps having a range of rated wattage (70–400 W). After estimation of the ‘quiet window’ of an HPSV lamp, the proposed iterative algorithm is able to determine the acoustic resonance-free driving frequencies of a design ballast corresponding to 50%–100% power level. On the other hand, a developed wattage and voltage independent HPSV lamp model facilitates finding the required electrical characteristics of HPSV lamps without performing laboratory experimentation. Using the estimated driving frequencies of a design ballast and the synthesized electrical characteristics of the lamp, the design circuit parameters of an electronic ballast are determined. Performance evaluation of the designed ballasts, carried out on the Matlab–Simulink platform, indicates several important attributes, viz. higher power control accuracy (deviation ≤3.69%), near-unity lamp power factor (≥0.98), lower lamp current crest factor (<1.7) and lower lamp current total harmonic distortion (≤12.63%). Results establish the effectiveness of the proposed design methodology to design lightweight and compact electronic ballasts for HPSV lamps with less effort than conventional design practice.

Acoustic communication in marine shallow waters: testing the acoustic adaptive hypothesis in sand gobies.

Acoustic communication is an important part of social behaviour of fish species that live or breed in shallow noisy waters. Previous studies have shown that some fish species exploit a quiet window in the background noise for communication. However, it remains to be examined whether hearing abilities and sound production of fish are adapted to marine habitats presenting high hydrodynamism. Here, we investigated whether the communication system of the painted (Pomatoschistus pictus) and the marbled (Pomatoschistus marmoratus) gobies is adapted to enhance sound transmission and reception in Atlantic shallow water environments. We recorded and measured the sound pressure levels of social vocalisations of both species, as well as snapshots of ambient noise of habitats characterised by different hydrodynamics. Hearing thresholds (in terms of both sound pressure and particle acceleration) and responses to conspecific signals were determined using the auditory evoked potential recording technique. We found that the peak frequency range (100-300 Hz) of acoustic signals matched the best hearing sensitivity in both species and appeared well adapted for short-range communication in Atlantic habitats. Sandy/rocky exposed beaches presented a quiet window, observable even during the breaking of moderate waves, coincident with the main sound frequencies and best hearing sensitivities of both species. Our data demonstrate that the hearing abilities of these gobies are well suited to detect conspecific sounds within typical interacting distances (a few body lengths) in Atlantic shallow waters. These findings lend support to the acoustic adaptive hypothesis, under the sensory drive framework, proposing that signals and perception systems coevolve to be effective within local environment constraints.

Congestion estimation technique in the optical network unit registration process.

We present a congestion estimation technique (CET) to estimate the optical network unit (ONU) registration success ratio for the ONU registration process in passive optical networks. An optical line terminal (OLT) estimates the number of collided ONUs via the proposed scheme during the serial number state. The OLT can obtain congestion level among ONUs to be registered such that this information may be exploited to change the size of a quiet window to decrease the collision probability. We verified the efficiency of the proposed method through simulation and experimental results.

Dispatches

Dispatches

Traffic noise masks acoustic signals of freshwater stream fish

In order for an acoustic signal to be an effective source of communication, the signal must be successfully detected and interpreted by the intended receiver. One potential barrier to acoustic communication is background noise. Lotic systems contain a wide variety of habitats including riffles, shoals and waterfalls that can become quite noisy. The increasing prevalence of road and train crossings over small streams, and increased boat traffic in navigable rivers and lentic systems also presents potential anthropogenic noise sources with which vocal fishes did not evolve. The present study investigates the relationship between vocalizations and the natural soundscape of a common fish of the Southeastern United States, the Blacktail Shiner (Cyprinella venusta), and the potential effects anthropogenic noise from bridge crossings may have on the soundscape and acoustic communication in this species. Results revealed a particularly close association of a quiet window in the natural soundscape of C. venusta and dominant frequencies of the courtship vocalization of C. venusta. Results also indicated that C. venusta’s acoustic signals propagate short distances, following predictions based on the calculated cutoff frequency of the streams they inhabit, and were masked by noise generated from bridge crossings. Our calculations suggest that road traffic noise propagates to an extent that virtually entire watersheds are impacted by this noise pollution, especially in urban areas.

Adaptive Registration in TWDM-PON With ONU Migrations

In time and wavelength division multiplexed passive optical networks (TWDM-PONs), optical network unit (ONU) migration (equivalently retuning working wavelength pairs) is an effective approach to reducing power consumption at the optical line terminal (OLT) side. Migration delay, the time from when a migration is initiated until the migrating ONU(s) have successfully joined the target wavelength pair, may affect the user service level agreement (SLA) and should be minimized. After an ONU migration process has been triggered, both the ONUs to be migrated (the migrating ONUs) and the newly incoming ones will have to register (referred to as activation in the ITU-T G.984.3 standard) in the upcoming quiet windows. This makes the number of ONUs competing in a single quiet window much more dynamic and leads to unpredictable registration performance and longer registration delay, which in turn will have a negative impact on the migration delay. In this paper, we propose an adaptive registration scheme in a TWDM-PON with ONU migrations. In the proposed scheme, the size of the quiet window is adaptively adjusted according to the up-to-date number of involved ONUs (including both ONUs to be migrated and the newly incoming ones). We show through simulations that the proposed scheme reduces average migration delay and increases the bandwidth utilization, especially when a large number of ONUs are involved in a registration process. In addition, we further investigate the length of the discovery cycle and find a shorter discovery cycle is needed to reduce migration delay and satisfy the requirement of the ONU SLA for a large number of involved ONUs. To realize a 99.999% ONU SLA, the length of the discovery cycle has to be shorter than 0.1 s for 128 involved ONUs and 0.15 s for 32 involved ONUs.

More than a blog

Last December, astrobiologists reported in the journal Science that they had discovered the first known microorganism on Earth capable of growing and reproducing by using arsenic (Wolfe‐Simon et al , 2010). While media coverage went wild, the paper was met with a resounding public silence from the scientific community. That is, until a new breed of critic, science bloggers, weighed in. Leading the pack was Rosie Redfield, who runs a microbiology research lab in the Life Sciences Centre at the University of British Columbia in Vancouver, Canada. She posted a critique of the research to her blog, RRResearch (rrresearch.fieldofscience.com), which went viral. Redfield said that her site, which is typically a quiet window on activities in her lab got 100,000 hits in a week. > Redfield said that her site, which is typically a quiet window on activities in her lab got 100,000 hits in a week This incident, like a handful before it and probably more to come, has raised the profile of science blogging and the freedom that the Internet offers to express an opinion and reach a broad audience. Yet it also raises questions about the validity of unfettered opinion and personal bias, and the ability to publish online with little editorial oversight and few checks and balances. Redfield certainly did not hold back in her criticism of the paper. Her post said of the arsenic study: “Lots of flim‐flam, but very little reliable information. […] If this data was presented by a PhD student at their committee meeting, I'd send them back to the bench to do more clean‐up and controls.” She also opined on why the article was published: “I don't know whether the authors are just bad scientists or whether they're unscrupulously pushing NASA's ‘There's life in outer space!’ agenda. I hesitate to blame the reviewers, …

Sounds of shallow water fishes pitch within the quiet window of the habitat ambient noise

The habitat ambient noise may exert an important selective pressure on frequencies used in acoustic communication by animals. A previous study demonstrated the presence of a match between the low-frequency quiet region of the stream ambient noise (termed 'quiet window') and the main frequencies used for sound production and hearing by two stream gobies (Padogobius bonelli, Gobius nigricans). The present study examines the spectral features of ambient noise in very shallow freshwater, brackish and marine habitats and correlates them to the range of dominant frequencies of sounds used by nine species of Mediterranean gobies reproducing in these environments. Ambient noise spectra of these habitats featured a low-frequency quiet window centered at 100 Hz (stream, sandy/rocky sea shore), or at 200 Hz (spring, brackish lagoon). The analysis of the ambient noise/sound spectrum relationships showed the sound frequencies matched the frequency band of the quiet window in the ambient noise typical of their own habitat. Analogous ambient noise/sound frequency relationships were observed in other shallow-water teleosts living in similar underwater environments. Conclusions may be relevant to the understanding of evolution of fish acoustic communication and hearing.

Stream ambient noise, spectrum and propagation of sounds in the goby Padogobius martensii: Sound pressure and particle velocity

The most sensitive hearing and peak frequencies of courtship calls of the stream goby, Padogobius martensii, fall within a quiet window at around 100 Hz in the ambient noise spectrum. Acoustic pressure was previously measured although Padogobius likely responds to particle motion. In this study a combination pressure (p) and particle velocity (u) detector was utilized to describe ambient noise of the habitat, the characteristics of the goby's sounds and their attenuation with distance. The ambient noise (AN) spectrum is generally similar for p and u (including the quiet window at noisy locations), although the energy distribution of u spectrum is shifted up by 50-100 Hz. The energy distribution of the goby's sounds is similar for p and u spectra of the Tonal sound, whereas the pulse-train sound exhibits larger p-u differences. Transmission loss was high for sound p and u: energy decays 6-10 dB10 cm, and sound pu ratio does not change with distance from the source in the nearfield. The measurement of particle velocity of stream AN and P. martensii sounds indicates that this species is well adapted to communicate acoustically in a complex noisy shallow-water environment.

Acoustic communication in two freshwater gobies: ambient noise and short-range propagation in shallow streams.

Noise is an important theoretical constraint on the evolution of signal form and sensory performance. In order to determine environmental constraints on the communication of two freshwater gobies Padogobius martensii and Gobius nigricans, numerous noise spectra were measured from quiet areas and ones adjacent to waterfalls and rapids in two shallow stony streams. Propagation of goby sounds and waterfall noise was also measured. A quiet window around 100 Hz is present in many noise spectra from noisy locations. The window lies between two noise sources, a low-frequency one attributed to turbulence, and a high-frequency one (200-500 Hz) attributed to bubble noise from water breaking the surface. Ambient noise from a waterfall (frequencies below 1 kHz) attenuates as much as 30 dB between 1 and 2 m, after which values are variable without further attenuation (i.e., buried in the noise floor). Similarly, courtship sounds of P. martensii attenuate as much as 30 dB between 5 and 50 cm. Since gobies are known to court in noisy as well as quiet locations in these streams, their acoustic communication system (sounds and auditory system) must be able to cope with short-range propagation dictated by shallow depths and ambient noise in noisy locations.

Seismic timing control system

A method for optimizing the acoustic signal-to-noise ratio during a useful maximal-length recording cycle within the time frame of a minimal-length recording episode. To implement the method, during an intermittent-tow seismic operation, the noise level due to cable manipulation during an entire recording episode is monitored. A quiet-window of a desired length is established by adjusting the length of the interval during which the seismic cable is at rest. The initiation of a recording cycle is adjusted relative to the quiet window to take maximum advantage of the quiet period.