{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/87110"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/87110","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"A photophonic instrument concept to measure atmospheric aerosol absorption","abstract":"A laboratory model of an instrument concept to measure the absorption of solar radiation by atmospheric aerosols was designed, built and tested. The concept was based on the photophonic phenomenon discovered by Bell and an acoustic resonator developed by Helmholtz. The design consisted of two chambers: an aerosol chamber and a reference chamber combined into a double Helmholtz resonator configuration. The radiation from the visible light source was amplitude modulated by a mechanical chopper. The modulated light beam was passed through the chambers and pressure variations resulted from energy absorbed by the aerosol in the chamber. The pressure signal was sensed by microphones, then the electrical signal amplified and processed by a differential amplifier. The testing showed the instrument had sufficient sensitivity and low enough system noise to measure an absorption coefficient of about 10⁻⁶/meter. Methods of signal improvement and noise reduction were discussed and tested. The results showed the instrument could measure absorption coefficients within the range expected by the earth's atmospheric aerosols. The instrument design was not optimized for maximum signal or minimum noise, but the justifiable conclusion was reached that the concept showed the promise of leading to a useful instrument in the measurement of atmospheric aerosol absorption and an improvement over the present instruments.","abstract_html":"A laboratory model of an instrument concept to measure the absorption of solar radiation by atmospheric aerosols was designed, built and tested. The concept was based on the photophonic phenomenon discovered by Bell and an acoustic resonator developed by Helmholtz. The design consisted of two chambers: an aerosol chamber and a reference chamber combined into a double Helmholtz resonator configuration. The radiation from the visible light source was amplitude modulated by a mechanical chopper. The modulated light beam was passed through the chambers and pressure variations resulted from energy absorbed by the aerosol in the chamber. The pressure signal was sensed by microphones, then the electrical signal amplified and processed by a differential amplifier. The testing showed the instrument had sufficient sensitivity and low enough system noise to measure an absorption coefficient of about 10⁻⁶/meter. Methods of signal improvement and noise reduction were discussed and tested. The results showed the instrument could measure absorption coefficients within the range expected by the earth's atmospheric aerosols. The instrument design was not optimized for maximum signal or minimum noise, but the justifiable conclusion was reached that the concept showed the promise of leading to a useful instrument in the measurement of atmospheric aerosol absorption and an improvement over the present instruments.","abstract_has_math":false,"creators":["Engle, Charles Dennis"],"institution":"Virginia Polytechnic Institute and State University","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Environmental Sciences and Engineering","degree_department":"Environmental Sciences and Engineering","school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":1982,"date_issued":"1982","date_published":"1982","updated_at":"2026-07-22T22:19:13Z","subjects":[],"languages":["en_US"],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/10919/87110","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.department","label":"Department","values":["Environmental Sciences and Engineering"]},{"key":"dc:creator","label":"Author","values":["Engle, Charles Dennis"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2019-01-31T17:50:25Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2019-01-31T17:50:25Z"]},{"key":"dc:date.issued","label":"Date","values":["1982"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Polytechnic Institute and State University"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.dcmitype","label":"Dc Type Dcmitype","values":["Text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Environmental Sciences and Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en_US"]},{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10919/87110"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["A laboratory model of an instrument concept to measure the absorption of solar radiation by atmospheric aerosols was designed, built and tested. The concept was based on the photophonic phenomenon discovered by Bell and an acoustic resonator developed by Helmholtz. The design consisted of two chambers: an aerosol chamber and a reference chamber combined into a double Helmholtz resonator configuration. The radiation from the visible light source was amplitude modulated by a mechanical chopper. The modulated light beam was passed through the chambers and pressure variations resulted from energy absorbed by the aerosol in the chamber. The pressure signal was sensed by microphones, then the electrical signal amplified and processed by a differential amplifier. The testing showed the instrument had sufficient sensitivity and low enough system noise to measure an absorption coefficient of about 10⁻⁶/meter. Methods of signal improvement and noise reduction were discussed and tested. The results showed the instrument could measure absorption coefficients within the range expected by the earth's atmospheric aerosols. The instrument design was not optimized for maximum signal or minimum noise, but the justifiable conclusion was reached that the concept showed the promise of leading to a useful instrument in the measurement of atmospheric aerosol absorption and an improvement over the present instruments."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["A photophonic instrument concept to measure atmospheric aerosol absorption"]}]}],"canonical_facts":{"dc:contributor.department":["Environmental Sciences and Engineering"],"dc:creator":["Engle, Charles Dennis"],"dc:date.accessioned":["2019-01-31T17:50:25Z"],"dc:date.available":["2019-01-31T17:50:25Z"],"dc:date.issued":["1982"],"dc:description.abstract":["A laboratory model of an instrument concept to measure the absorption of solar radiation by atmospheric aerosols was designed, built and tested. The concept was based on the photophonic phenomenon discovered by Bell and an acoustic resonator developed by Helmholtz. The design consisted of two chambers: an aerosol chamber and a reference chamber combined into a double Helmholtz resonator configuration. The radiation from the visible light source was amplitude modulated by a mechanical chopper. The modulated light beam was passed through the chambers and pressure variations resulted from energy absorbed by the aerosol in the chamber. The pressure signal was sensed by microphones, then the electrical signal amplified and processed by a differential amplifier. The testing showed the instrument had sufficient sensitivity and low enough system noise to measure an absorption coefficient of about 10⁻⁶/meter. Methods of signal improvement and noise reduction were discussed and tested. The results showed the instrument could measure absorption coefficients within the range expected by the earth's atmospheric aerosols. The instrument design was not optimized for maximum signal or minimum noise, but the justifiable conclusion was reached that the concept showed the promise of leading to a useful instrument in the measurement of atmospheric aerosol absorption and an improvement over the present instruments."],"dc:description.degree":["Master of Science"],"dc:format.mimetype":["application/pdf"],"dc:identifier.uri":["http://hdl.handle.net/10919/87110"],"dc:language.iso":["en_US"],"dc:publisher":["Virginia Polytechnic Institute and State University"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:title":["A photophonic instrument concept to measure atmospheric aerosol absorption"],"dc:type":["Thesis"],"dc:type.dcmitype":["Text"],"thesis:degree_discipline":["Environmental Sciences and Engineering"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:19:13Z"}