IEC/TR 62781:2012(E), which is a technical report, is applicable to all measurements of ultrasonic fields where water is the transmission medium. Water provides an inexpensive and readily available medium with characteristic acoustic impedance comparable to biological tissue. However, basic tap water is far from optimum for ultrasonic measurement as it contains many dissolved, absorbed and suspended contaminants. Measurements can be affected in many ways by these impurities. This technical aims to provide a unified source to establish a water treatment process for ultrasonic measurements. The quality and treatment methods for water used within a radiation force balance (RFB) may be different from that required for hydrophone based acoustic measurements. Chemical based methods of water treatment (e.g. algaecides) may be appropriate for these applications. However, in this document, chemical means are noted but appropriately discouraged for acoustic pressure/intensity measurements. This Technical Report describes methods for:
- degassing water to be used in ultrasonic measurements;
- to decrease the ionic content of water to be used in ultrasonic measurements;
- to decrease the biological content of water to be used in ultrasonic measurements; and
- to reduce the suspended particulate content of water to be used in ultrasonic measurements.