@prefix cpm: . @prefix dc: . @prefix dcat: . @prefix dce: . @prefix dct: . @prefix grg: . @prefix iop: . @prefix ns0: . @prefix ns1: . @prefix owl: . @prefix pav: . @prefix prov: . @prefix puv: . @prefix qudt: . @prefix rdf: . @prefix rdfs: . @prefix reg: . @prefix semapv: . @prefix skos: . @prefix sssom: . @prefix void: . skos:broader . skos:narrower . skos:narrower . skos:altLabel "" ; skos:broader ; skos:definition "Marine seismic sources that send sound pulses into the sub-sea floor sediments. The sound pulses bounce off the sea floor and subsequent buried sediment layers according to differences in their acoustic impedance (hardness) and in turn, their density. Pingers are linear, single channel, high frequency systems that typically operate at frequencies greater than 2 kHz and penetrate to several tens of metres."@en ; skos:inScheme ; skos:narrower , , , ; skos:notation "SDN:L05::394" ; skos:note "accepted"@en ; skos:prefLabel "Pinger sub-bottom profilers"@en . skos:broader . skos:broader . skos:broader . skos:broader . skos:broader . skos:broader . skos:broader . skos:member .