Virtual bass preprocessing and carrier frequency optimization for the parametric array loudspeaker

The parametric array loudspeaker (PAL) is a novel type of loudspeaker that can project a directional sound beam. It is usually used in creating personal sound zone and projecting private messages to a targeted audience. However, the PAL has a very poor low-frequency response due to the inherent nonlinear acoustic principle generating sound from ultrasound in air. A psychoacoustic signal processing method known as the virtual bass (VB) has been proved to be an effective method to improve the bass quality of consumer electronics with miniature or flat loudspeaker unit. This paper proposes the VB processing based on the phase vocoder (PV) for the bass enhancement of the PAL that adopts a vestigial sideband modulation method. The harmonics generated by the VB processing are presented in the partial sideband, while the audio input without the bass component is embedded in the full sideband. A measure, namely the in-band peak flatness, is thereafter proposed in this paper to determine the optimal carrier frequency, given a practical uneven frequency response of the ultrasonic transducer. The subjective testing results validate that the proposed VB processing together with the optimal carrier frequency can finally realize the improvement of bass sound quality of the PAL.

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Low-Frequency Response of Hearing Aids and Judgments of Aided Speech Quality

Journal of Speech and Hearing Disorders ◽

10.1044/jshd.4503.325 ◽

1980 ◽

Vol 45 (3) ◽

pp. 325-335 ◽

Cited By ~ 20

Author(s):

Jerry L. Punch ◽

Edwin L. Beck

Keyword(s):

Frequency Response ◽

Hearing Aids ◽

Paired Comparison ◽

Hearing Aid ◽

Cutoff Frequency ◽

Low Frequency ◽

Hearing Impaired ◽

Connected Discourse ◽

Experimental Trials

Connected discourse was processed by a master hearing aid via two channels that were independently adjusted to seven discrete settings of low-cutoff frequency. Signals were tape-recorded and played back in a paired-comparison format to 12 listeners with gradually sloping sensorineural hearing loss, who selected the speech channel preferred for its sound quality. Four experimental trials were administered, each of which consisted of 21 randomized paired conditions. Results across the four trials revealed high intersubject and intrasubject response agreement. Listeners indicated strong and systematic preferences for speech reproduced by circuitry having progressively extended low-frequency emphasis. Findings confirm earlier experimental observations that hearing-impaired listeners are capable of making repeatable paired-comparison preference judgments of the quality of hearing-aid processed speech. Additionally, results demonstrate definitively that low-cutoff frequency is sufficiently robust to be regarded as the probable source of a potent perceptual basis for such judgments. The clinical implication is that hearing-impaired listeners can be expected to exhibit strong preferences for the quality of speech reproduced by hearing aids having relatively extended low-frequency response.

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Directional Loudspeaker Using a Parametric Array

Acta Polytechnica ◽

10.14311/862 ◽

2006 ◽

Vol 46 (4) ◽

Author(s):

A. Ritty

Keyword(s):

Carrier Frequency ◽

Nonlinear Acoustics ◽

Finite Amplitude ◽

Sound Beam ◽

Sound Reproduction ◽

Audible Sound ◽

Parametric Array ◽

Film Transducer

The theory for sound reproduction of parametric arrays is based on nonlinear acoustics. Due to the nonlinearity of the air, a finite amplitude ultrasound interacts with itself and generates audible secondary waves in the sound beam. A special feature of this loudspeaker is its sharper directivity compared to conventional loudspeakers of the same aperture size.This paper describes the basis of the theory used for parametric arrays, and presents the influence of the main parameters, e.g., carrier frequency. It also describes some signal pre-processing needed to obtain the desired audible sound. A PVDF (polyvinylidenefluoride) film transducer is also studied in order to produce a prototype to confirm the theory.

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Dynamics of the processes in metal machining

Nonlinear Analysis Modelling and Control ◽

10.15388/na.1998.2.0.15295 ◽

1998 ◽

Vol 2 ◽

pp. 115-122

Author(s):

Donatas Švitra ◽

Jolanta Janutėnienė

Keyword(s):

High Frequency ◽

Machine Tools ◽

Metal Cutting ◽

Cutting Tool ◽

Low Frequency ◽

Metal Cutting Machine ◽

Cutting Machine ◽

Metal Machining

In the practice of processing of metals by cutting it is necessary to overcome the vibration of the cutting tool, the processed detail and units of the machine tool. These vibrations in many cases are an obstacle to increase the productivity and quality of treatment of details on metal-cutting machine tools. Vibration at cutting of metals is a very diverse phenomenon due to both it’s nature and the form of oscillatory motion. The most general classification of vibrations at cutting is a division them into forced vibration and autovibrations. The most difficult to remove and poorly investigated are the autovibrations, i.e. vibrations arising at the absence of external periodic forces. The autovibrations, stipulated by the process of cutting on metalcutting machine are of two types: the low-frequency autovibrations and high-frequency autovibrations. When the low-frequency autovibration there appear, the cutting process ought to be terminated and the cause of the vibrations eliminated. Otherwise, there is a danger of a break of both machine and tool. In the case of high-frequency vibration the machine operates apparently quiently, but the processed surface feature small-sized roughness. The frequency of autovibrations can reach 5000 Hz and more.

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Estimating the Quality of Thermionic Cathodes for Microwave Vacuum Tubes Using the Low-Frequency Noise Parameters

Vestnik MEI ◽

10.24160/1993-6982-2018-5-120-127 ◽

2018 ◽

Vol 5 (5) ◽

pp. 120-127

Author(s):

Mikhail D. Vorobyev ◽

◽

Dmitriy N. Yudaev ◽

Andrey Yu. Zorin ◽

◽

...

Keyword(s):

Low Frequency ◽

Frequency Noise ◽

Low Frequency Noise ◽

Noise Parameters ◽

Thermionic Cathodes ◽

Vacuum Tubes

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MULTISTAGE MICROSTRIP UHF LOAD

Issues of radio electronics ◽

10.21778/2218-5453-2018-4-53-57 ◽

2018 ◽

pp. 53-57 ◽

Cited By ~ 2

Author(s):

G. G. Savenkov ◽

V. P. Razinkin ◽

A. D. Mekhtiev

Keyword(s):

Frequency Response ◽

Frequency Band ◽

High Power ◽

Two Stage ◽

High Power Microwave ◽

Modelling Method ◽

Optimal Values ◽

Inductive Elements ◽

Power Microwave

Applications of modern terminal loads and its relevant disadvantages are described in this paper. The decomposing method of wideband microwave high power microstrip loads design is proposed in this paper with purpose of matching quality improving. Multiple extension of multistage load bandwidth is provided by using of external matching circuit and internal matching inductive elements. The maximum reachable bandwidth of multistage load is estimated and optimal values of mathing circuit elements are founded on basis of equivalent lumped scheme. The topology of microstrip two-stage high power microwave load is developed and its frequency response, calculated via numeric electrodynamic modelling method is outlined in the paper. Modelling results show good matching quality of considered load at the frequency band below 3,5 GHz.

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