An interesting paper was published in 2013 in the journal PLoS ONE about sounds emitted by microgastrine wasps: "Characterization and generation of male courtship song in Cotesia congregata (Hymenoptera: Braconidae). The paper included among its Supporting Information one audio-recording and two high-speed videos of the courtship song of a male of Cotesia congregata.
Parasitoid wasps have been long known to produce sounds. The earliest paper in the scientific literature I could find was from 40 years ago, and it dealt with an ichneumonid wasp (Vinson S.B. 1972: Courtship behavior and evidence of a sex pheromone in the parasitoid Campoletis sonorensis (Hymenoptera: Ichneumonidae). Environ Entomol 1: 409–414).
The earliest paper that specifically referred to sounds emitted by a microgastrine wasp was published 20 years ago (Field S.A. Keller M.A. 1993: Courtship and intersexual signaling in the parasitic wasp Cotesia rubecula (Hymenoptera: Braconidae). J Insect Behav 6: 737–750. doi: 10.1007/BF01201673). After that, there have been a handful of papers (mostly but not exclusively using the genus Cotesia as a model) published. Hopefully more studies on the topic will follow.
Sounds in these wasps are mainly related to mating. The dynamic of sound transmission, and its effects on the behaviour of both male and female wasps, is nothing short of remarkable.
One of the figures of the PLOS ONE paper mentioned. The caption of the original figure actually reads: "Figure 1. Oscillograph of typical male courtship song of Cotesia congregata with a buzz followed by boings.(A) Complete song. (B) Expanded selection of initial buzz. (C) Expanded selection of four boings illustrating the initial high amplitude component followed by a lower amplitude terminal buzz and short gap.doi:10.1371/journal.pone.0062051.g001"
[This post is an expanded article based on a post from a blog on Microgastrinae wasps (http://cncbraconidae.blogspot.ca/) that used to be written by one of us (Jose Fernandez-Triana). That blog is no longer active but its contents have been moved to this website].