Spacecraft Acoustics and Noise Control Practice Flashcards

These flashcards provide vocabulary definitions and technical specifications regarding spacecraft acoustics, noise control methods, and specific mission hardware for the ISS and Apollo programs.

Speech Interference Level (SIL)

The average sound pressure level across octave bands centered at $1000$, $2000$, and $4000\,Hz$.

Tonal or Musical Noise Requirement

Narrowband components must be a minimum of $10\,dB$ below the containing octave band.

Continuous Noise (NASA Definition)

Noise that lasts for more than $8\,\text{hours}$ in a $24\text{-hour}$ period.

Maximum Launch/Entry Noise Exposure

The maximum allowable noise exposure during launch, entry, and cabin pressure events, capped at $105\,\text{dBA}$.

Statistical Energy Analysis (SEA)

A tool or method used for conducting acoustic simulations in complex systems during the design phase.

Analysis & Design Step

The phase in the Noise Control Plan that involves ranking noise sources and mapping source-to-receiver paths.

External Sound Control Methods

Methods used around noise sources including wraps, covers, and barriers.

Active Hearing Protection

A type of protection that reduces noise electronically and is often integrated into headsets.

Anti-Vibration Mount (AVM) Modes

The two modes used to improve isolation performance based on gravity conditions: Locked AVM and Unlocked AVM.

Environmental Control System (ECS)

The spacecraft system responsible for providing life support and thermal control, often a major noise source.

Suit Compressor

A component identified as a major contributor to high cabin noise levels in both the Apollo Command Module and the Lunar Module.

Apollo Non-stressed Noise Limit

The noise limit for Overall Sound Pressure Level (OASPL) set in the 1963 Apollo Master Spacecraft Specification, which was $80\,dB$.

Emergency Noise Limit

The maximum noise level allowed for approximately $10\,\text{seconds}$, defined as $143\,dB$.

Lunar Module (LM) Stages

The two main stages of the module: the Ascent stage and the Descent stage.

Vane Passage Frequency (VPF)

The dominant noise peak created by the LM glycol pumps, which operated at $6,000\,rpm$ with four vanes, resulting in a peak at $400\,Hz$.

Expansion Chamber Muffler

The specific muffler design with an inlet and outlet offset selected to reduce glycol pump noise in the Lunar Module.

NASA Acoustics Lead

The central manager who oversees and coordinates all acoustic efforts and chairs the Acoustics Working Group (AWG).

Sound Level Meter

Hardware used to measure continuous acoustic levels and frequency spectra.

Russian State Standards (GOST)

The acoustic standards followed by the Russian Segment of the ISS.

Vozdukh

The $CO_2$ removal system located on the Service Module of the ISS.

Functional Cargo Block (Zarya)

The first International Space Station module placed into orbit.

Kayutas

The designated sleeping quarters located on the ISS Service Module.

Temporary Early Sleep Station (TeSS)

A quieter sleeping area installed in the U.S. Lab, designed with panels composed of Fibrelam® honeycomb with an aramid core and carbon fiber skin.

Destiny

The first laboratory module of the International Space Station contributed by the United States.

Common Cabin Air Assembly (CCAA)

The system responsible for maintaining the cabin environment within ISS modules.

Quest Airlock

The U.S. module primary function is for spacewalk operations (EVA), which required an operational noise limit of $65\,\text{dBA}$.

Kibo

The Japanese Experiment Module, meaning "Hope," consisting of the Pressurized Module, Exposed Facility, Experiment Logistics Module, Remote Manipulator System, and Inter-orbit Communication System.

Columbus Laboratory

The ESA contributed laboratory that serves as a hub for biology and fluid physics research.

Node 2 (Harmony)

The ISS module described as the "Gateway" connecting laboratories from three different continents.

MELFI Cold Box Noise

Severe high-frequency noise caused by a Brayton machine operating at $92,000 - 96,000\,rpm$.

PGBA (Plant Generic Bio-processing Apparatus)

A payload whose inlet muffler achieved a $28\,dB$ reduction at the $8000\,Hz$ band.