What Is Sound Pressure Level?

Sound pressure level (SPL) is a measure of the pressure variation, relative to a reference value, caused by a sound wave. It is measured using a sound pressure level meter in units of pressure in decibels (dB). SPL is a crucial parameter in fields such as environmental noise monitoring, audio engineering, and product testing.

The reference value used for sound pressure level is 20 micropascals, which is the threshold of human hearing for a 1 kHz sinusoidal tone. The nonlinear sensitivity of the human auditory system motivates the use of decibels. The human ear also has a frequency-dependent sensitivity, so frequency weighting is commonly used in SPL measurement.

You can use MATLAB^® and Audio Toolbox™ to compute sound pressure level measurements with A, C, and Z weighted frequency filters. The specific sound pressure measurement that you want to use will depend on the application you are designing for. Time-weighted sound levels, equivalent-continuous sound levels, peak sound levels, and maximum time-weighted levels have different importance when it comes to meeting occupational noise standards versus evaluating the quality of a consumer electronics product. The splMeter System object™ measures these levels and provides frequency-weighted sound pressure levels.

Sound Pressure Level Applications

SPL measurements are used in many applications, including:

• Environmental noise monitoring: Prolonged exposure to high noise levels can lead to hearing loss, stress, and other health issues. Noise pollution can also adversely affect wildlife. These effects make sound pressure level measurement critical to planning work environments, residential and urban areas, schools, and hospitals. Many countries have regulations and standards that specify permissible noise levels in different environments.
• Audio engineering: SPL measurements help in monitoring and controlling the volume of sound to prevent hearing damage in both live and studio environments. Accurate SPL measurements enable engineers to balance different audio elements, ensuring that vocals and instruments are heard clearly without distortion. In the design of studios, concert halls, and other venues, sound pressure measurements are used to assess and optimize the acoustic properties of a space.
• Product testing: Excessive noise can be harmful to product users, who also may associate noise levels with the quality of a product. SPL measurements enable objective comparison of similar products, providing valuable data for both product developers and consumers.