Compost Biology and Acoustics

Impact of microwaves and water on acoustical signatures of a compost

Sounds and Spectograms

The acoustics of four states of a compost were analyzed.   Compost (200 cm3), made from leaves and kitchen refuse, with its natural biota (earthworms, Isopods, Collembola, Staphilinid beetles, nematodes and other microscopic organisms) was placed in two 400 ml glass containers.  One was microwaved in a “Sharp Carousel R-326FS” model microwave for two minutes, with an output power of 1100W, and the frequency 2450 MHz.  A hydrophone (Aquarian AQ3) was place on a 35° angle on the compost surface in both containers and the sounds recorded for 30 seconds in a sound-insulated chamber.  The process was repeated five times.  Subsequently, 50 ml of water was added to both the original and microwaved compost. The resulting acoustics were recorded as described above.  The compost was moist (~40% moisture) and at room temperature (~21 Co). The activities of the macro-invertebrates were also visually observed.

Sounds of Compost (non-microwaved) with water added as an activating agent (to hear the sound click on the replication number): replication 1, 2, 3, 4, 5 and 6

Sounds of compost (non-microwaved) without water added: replication 1, 2, 3, 4, and 5

Sounds of microwaved compost with water added: replication 1, 2, 3, 4, and 5

Sounds of microwaved compost without water added: replication 1, 2, 3, 4, and 5

Fig 1 sonograms

Fig 1.  Sonograms (spectrograms) of sounds of non-microwaved and microwaved compost with and without water as an activating agent.  The x axis is 30 seconds time and the y axis represents kHz levels 1-2.  The color intensity and brightness indicates loudness. Replicates one are shown in the sonograms.

Michigan State University
  • Spartans Will.
  • © Michigan State University

MSU is an affirmative-action, equal-opportunity employer, committed to achieving excellence through a diverse workforce and inclusive culture that encourages all people to reach their full potential.

Michigan State University Extension programs and materials are open to all without regard to race, color, national origin, gender, gender identity, religion, age, height, weight, disability, political beliefs, sexual orientation, marital status, family status or veteran status. Issued in furtherance of MSU Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Quentin Tyler, Director, MSU Extension, East Lansing, MI 48824. This information is for educational purposes only. Reference to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned.

The 4-H Name and Emblem have special protections from Congress, protected by code 18 USC 707.

We comply with the Federal Trade Commission 1998 Children’s Online Privacy Protection Act (COPPA).