Search NASA⌕ Search

Engineering topics

Slazak, M.

Publications and source records attributed to Slazak, M..

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Design of sidewall treatment of cabin noise control of a twin engine turboprop aircraft

An analytical procedure was used to predict the noise transmission into the cabin of a twin engine general aviation aircraft. This model was then used to optimize the interior A weighted noise levels to an average value of about 85 dBA. The surface pressure noise spectral levels were selected utilizing experimental flight data and empirical predictions. The add on treatments considered in this optimization study include aluminum honeycomb panels, constrained layer damping tape, porous acoustic blankets, acoustic foams, septum barriers and limp trim panels which are isolated from the vibration of the main sidewall structure. To reduce the average noise level in the cabin from about 102 kBA (baseline) to 85 dBA (optimized), the added weight of the noise control treatment is about 2% of the total gross takeoff weight of the aircraft.

Vaicaitis, R.↗
NASA NTRS1982

Cabin Noise Control for Twin Engine General Aviation Aircraft

An analytical model based on modal analysis was developed to predict the noise transmission into a twin-engine light aircraft. The model was applied to optimize the interior noise to an A-weighted level of 85 dBA. To achieve the required noise attenuation, add-on treatments in the form of honeycomb panels, damping tapes, acoustic blankets, septum barriers and limp trim panels were added to the existing structure. The added weight of the noise control treatment is about 1.1 percent of the total gross take-off weight of the aircraft.

Vaicaitis, R.↗
NASA NTRS1981

Laboratory study of efficient add-on treatments for interior noise control in light aircraft

Experimental and theoretical studies of the transmission loss (TL) of 1.15 x 1.46 m flat stiffened-skin aluminum panels are described. Panel configurations included panels with no treatment and eight combinations of treatments consisting of a fiberglass-septum layer, a foam-foil damping material, and a plywood double wall trim panel. Measured TL of the untreated panel and the panel with a damping layer showed characteristics of the double mass law: at low frequencies the TL followed a mass law trend associated with the average mass of both skin and stiffness, while at higher frequencies the TL followed a mass law trend associated with skin mass only. A comparison of TL for panels treated with a damping layer, a fiberglass layer, or a trim panel showed that the effects of damping are frequency dependent with some performing better below 500 Hz and others performing better above 500 Hz. Treatment combinations showed that two treatments with the same mass could have TL values different by about 10 dB, while other combinations having weights different by a factor of two could have TL values within a few dB over most of the frequency range. The highest TL values (50 dB at 1000 Hz) were obtained with a treatment consisting of a fiberglass layer, a trim panel, and damping layers on both the stiffened panel and the trim panel.

Mixson, J. S.↗
NASA NTRS1981

Noise transmission and attenuation for business aircraft

This paper describes analytical studies applicable for estimating the effects of noise transmission into light aircraft and commuter type aircraft. The propeller noise and turbulent boundary layer noise are considered. The analytical model described uses modal methods and incorporates flat stiffened panels for flat sided sidewalls and curved stiffened panels for cylindrical enclosures. The numerical results include noise attenuation with add-on treatments and the sensitivity of the transmitted noise to the discrete stiffening of the sidewall panels.

Vaicaitis, R.↗
NASA NTRS1981

Response of stiffened sandwich panels

An increasingly important part of the design of skin-stringer systems, such as those found in flight vehicles, is the ability to reduce surface vibration levels when they are subjected to the dynamic loads of jet, or propeller noise. One common method of reducing the response of these structures is by layered construction using viscoelastic materials. Thus analytical methods to describe such systems are essential.

Slazak, M.↗
NASA NTRS1980

Noise transmission through stiffened panels

An analytical study is presented to predict low frequency noise transmission through finite stiffened panels into rectangular enclosures. Noise transmission is determined by solving the acoustic wave equation for the interior noise field and stiffened panel equations for vibrations of panels and stringers. The solution to this system of equations is obtained by a Galerkin-like procedure where the modes and frequencies for stiffened panels are determined by the transfer matrix method. Results include a comparison between theory and experiment and noise transmission through the sidewall of an aircraft.

Vaicaitis, R.↗
NASA NTRS1980

Noise transmission and attenuation by stiffened panels

An analytical study of noise transmission into semi-cylindrical and rectangular acoustic enclosures due to turbulent boundary layer pressure and propeller noise (prop-fan) is presented. The structural noise transmission models include a single panel, discretely stiffened elastic panel and stiffened viscoelastic sandwich panel. Response characteristics of the stiffened panels are evaluated using a transfer matrix procedure. The interior noise field is determined by a Galerkin-like method. The effect on interior noise due to aerodynamic surface flow, cavity back-up pressure, pressurization, mass, stiffness, and damping addition to the structure is investigated. It is shown that stiffened viscoelastic sandwich panels, while providing the same stiffening benefits as an equivalent elastic panel, could significantly reduce vibration levels and subsequently give similar benefits for interior noise control.

Vaicaitis, R.↗
NASA NTRS1979

Noise transmission - Turboprop problem

An analytical model is presented to predict low frequency (1000 Hz and below) noise transmission into aircraft. Noise transmission is determined by solving the acoustic wave equation for the interior noise field, the equivalent 'smeared' monocoque shell equation for overall fuselage vibrations and skin-stringer panel equation for local vibrations of panels and stringers. The solution to this system of equations is obtained by using a Galerkin-like procedure. The modes and frequencies for skin-stringer panels are determined by a transfer matrix method. Results include noise transmission through discretely stiffened panels and cabin noise due to turbulent boundary layer and propeller passage harmonics for a turboprop type aircraft.

Vaicaitis, R.↗