Abstract: An inlet ice protection system, and methods for making and using ice protection systems. In one embodiment, the inlet includes a tapered acoustic liner positioned forward of the inlet throat and has a perforated face sheet, a perforated back sheet, and an acoustic core between the face sheet and the back sheet. The perforations through the face sheet are sized to allow acoustic energy to be transmitted to and dissipated in the acoustic core, and the perforations in the back sheet are sized to transmit hot gas through the acoustic liner to the surface of the inlet to heat the inlet and prevent and/or restrict ice formation on the inlet. The face sheet can have a higher porosity than the back sheet, and both the sheets and the core can be formed from titanium to withstand high gas temperatures.

Abstract: An inlet ice protection system, and methods for making and using ice protection systems. In one embodiment, the inlet includes an acoustic liner positioned forward of the inlet throat and has a perforated face sheet, a perforated back sheet, and an acoustic core between the face sheet and the back sheet. The perforations through the face sheet are sized to allow acoustic energy to be transmitted to and dissipated in the acoustic core, and the perforations in the back sheet are sized to transmit hot gas through the acoustic liner to the surface of the inlet to heat the inlet and prevent and/or restrict ice formation on the inlet. The face sheet can have a higher porosity than the back sheet, and both the sheets and the core can be formed from titanium to withstand high gas temperatures.

Abstract: An inlet ice protection system, and methods for making and using ice protection systems. In one embodiment, the inlet includes an acoustic liner positioned forward of the inlet throat and has a perforated face sheet a perforated back sheet, and an acoustic core between the face sheet and the back sheet. The perforations through the face sheet are sized to allow acoustic energy to be transmitted to and dissipated in the acoustic core, and the perforations in the back sheet are sized to transmit hot gas through the acoustic liner to the surface of the inlet to heat the inlet and prevent and/or restrict ice formation on the inlet. The face sheet can have a higher porosity than the back sheet, and both the sheets and the core can be formed from titanium to withstand high gas temperatures.

Abstract: A portable acoustic impedance data acquisition and processing system is provided for use with a test object. The system includes a dynamic signal analyzer, a test head, a removable microphone holder, a cylindrical endcap fitting, an amplifier, and one or more power supply sources. The test head includes a compression driver and a cylindrical waveguide tube. The waveguide tube has a first end connected to the compression driver and a second end that is open. The removable microphone holder is attachable to the waveguide tube near its second end and a number of microphones are insertable into the microphone holder. During use, the dynamic signal analyzer provides audio output test signals that are amplified by the amplifier and fed to the compression driver for use as the acoustic test signal. The microphones provide measured signals to the dynamic signal analyzer which analyzes them and makes the results available to the operator.

Abstract: A method of forming an acoustic attenuation chambers within a honeycomb core. The honeycomb core have a plurality of honeycomb cells having interconnected side walls. A plurality of septum layers are spaced from one another within the honeycomb cells to define acoustic attenuation chambers between the septum layers and the side walls of the honeycomb cells. Each of the septum layers have an associated ablating wavelength and is transparent to the ablating wavelengths of the other septum layers. A laser beam having a laser wavelength is directed towards the septum layers. The laser beam is selectively absorbed by a septum layer which has an associated ablating wavelength equal to the laser wavelength to ablate apertures therethrough without ablating other septum layers.

Abstract: In accordance with the present invention, there is provided a method of forming an acoustic attenuation chambers within a honeycomb core. The honeycomb core have a plurality of honeycomb cells having interconnected side walls. A plurality of septum layers are spaced from one another within the honeycomb cells to define acoustic attenuation chambers between the septum layers and the side walls of the honeycomb cells. Each of the septum layers have an associated ablating wavelength and is transparent to the ablating wavelengths of the other septum layers. A laser beam having a laser wavelength is directed towards the septum layers. The laser beam is selectively absorbed by a septum layer which has an associated ablating wavelength equal to the laser wavelength to ablate apertures therethrough without ablating other septum layers.

Abstract: A high efficiency broadband acoustic resonator and absorption panel used for reducing engine noise from high bypass fan jet engines mounted on an aircraft. The panel uses a single layer of cellular honeycomb core with a pair of parallel acoustic septums formed internally in the core for attenuating high and medium frequency sounds during all engine operations as well as the low frequency combination tone and "buzzsaw" noise experienced during high power aircraft takeoff and cutback engine power settings.