Performance of an Inertially Coupled, 3-Mode Gravitational-Wave Antenna Prototype

A prototype three‐mode gravitational wave antenna which employs a two‐mode torsional transducer has been constructed and tested. For the torsional transducer the coupling from one stage to the next is via inertial forces, whereas in a conventional transducer the stage‐to‐stage coupling is proportional to the relative displacements via the springs. Experiments with our antenna‐torsional transducer prototype demonstrate a maximum antenna bandwidth of 260 Hz (29% of the antenna resonant frequency of 900 Hz) and a mechanical amplification factor of 40. A mathematical model for the three‐mode antenna has been developed and predictions of the system transfer functions and transient response are in close agreement with the measurements. Through the optimization of the transducer parameters we find that maximum fractional antenna bandwidths near 30% may be simultaneously achieved with mechanical amplification factors of 100 or more. Furthermore, the torsional transducer has a larger mechanical gain‐antenna bandwidth product than a linear transducer with similar masses

Design of an RSFQ Control Circuit to Observe MQC on an rf-SQUID

We believe that the best chance to observe macroscopic quantum coherence (MQC) in a rf-SQUID qubit is to use on-chip RSFQ digital circuits for preparing, evolving and reading out the qubit's quantum state. This approach allows experiments to be conducted on a very short time scale (sub-nanosecond) without the use of large bandwidth control lines that would couple environmental degrees of freedom to the qubit thus contributing to its decoherence. In this paper we present our design of a RSFQ digital control circuit for demonstrating MQC in a rf-SQUID. We assess some of the key practical issues in the circuit design including the achievement of the necessary flux bias stability. We present an "active" isolation structure to be used to increase coherence times. The structure decouples the SQUID from external degrees of freedom, and then couples it to the output measurement circuitry when required, all under the active control of RSFQ circuits. Research supported in part by ARO grant # DAAG55-98-1-0367.Comment: 4 pages. More information and publications at http://www.ece.rochester.edu:8080/users/sde/research/publications/index.htm

Radio-Frequency Superconducting Parametric Transducer for Gravitational-Wave Antennae

We report on the design and testing of an ultrasensitive, electromechanical transducer for use on resonant mass gravitational wave antennae. The transducer is a superconducting, radio frequency resonant bridge circuit operating near 200 MHz. We have minimized several important sources of noise in this transducer system. The Johnson noise of the transducer circuit is reduced through using a superconducting niobium stripline circuit and low‐loss insulating materials. At a temperature of 4.2 K we have achieved unloaded electrical quality factors of 200 000. The bridge circuit is balanced by piezoelectric actuators which control the spacing between the proof mass and capacitive segments of the stripline circuit and we have achieved a residual bridge imbalance of 3×10−7. Finally, low noise cryogenically cooled field‐effect transistors are used for the first amplifier stage, enabling us to obtain an amplifier noise level which is 5400 times the quantum limit. The transducer, which has a 0.080 kg proof mass, was affixed to the end of a prototype, resonant bar, gravitational wave antenna with a mass of approximately 100 kg. The primary purpose of this small antenna was to evaluate the transducer, which is designed to be mounted on a much more massive antenna. Our theoretical analysis and measurements of the detector agree and indicate a burst noise temperature of 1.8 K using the 100 kg bar. This corresponds to a gravity wave burst sensitivity of h=1.1×10−16, in terms of relative strain amplitude. With no other improvements, if the transducer mechanically resonant frequency were tuned to and installed on a 2000 kg antenna, the antenna would reach a noise temperature of 1.3 mK, which is equivalent to a gravitational wave burst sensitivity, h≊5.7×10−19

Pitch bends and tonguing articulation in clarinet physical modeling synthesis

A physical modeling approach is used to investigate play-ing effects in woodwind instruments. This builds upon prior work concerning both empirical studies of the acoustics of the clarinet and extensive development of computer simulations of musical instrument systems. Specifically, explicit imple-mentations of two performance gestures for the clarinet are given and demonstrated: tonguing and pitch bending. Phys-ical modeling for the clarinet is briefly reviewed. Following this we show how both tonguing and pitch bending map to changes in the clarinet physical model itself and in the control parameter data. To our knowledge, tonguing in particular is one effect that has not been widely discussed in the literature, at least in the exact form we present. Finally, some possible future research directions are indicated. Index Terms — music, modeling, signal synthesis 1

An energy conservation method for wireless sensor networks employing a blue noise spatial sampling technique

In this work, we consider applications of wireless sensor networks where a spatially band-limited physical phenomenon (e.g., temperature, pressure, low-frequency vibrations) can be sufficiently monitored by a subset o

Time-frequency Test Signal Synthesis for Acoustic Measurements During Music Concerts

When occupied by an audience, a musical performance space exhibits different acoustic characteristics compared to when it is empty. To obtain acoustical measurements with an audience present would require them to sit through an entire session of acoustic test signals, which is not practical. The dynamics of room acoustics parameters during an on-going concert may also be important to the mixing and recording engineers. These acoustic measurement scenarios demand an analysis tool for performing the designated tests during music concert sessions while not being noticeable by the audience. An acoustic measurement technique employing test signals generated during a musical performance is proposed. This method employs an adaptive time-frequency synthesis algorithm that determines the energy vacancies in the spectrogram of the on-going performance and automatically generates low-energy test signals that fill in the vacancies. The energy level of the test signal can be low enough to be masked by the music while high enough to be measurable above the noise floor. Several classes of test signals are proposed and their implementations in live musical events are demonstrated. Different system identification methods for estimating architectural acoustics parameters from the recorded test signals are also discussed and compared