Core Summary
Sound Pressure Level (SPL), expressed in decibels (dB), measures the loudness of sound and is an essential parameter when selecting alarms and buzzers. It involves a reference distance and a weighting method, making it easy to misjudge based on just one number. Understanding these two points allows for a consistent comparison of "loudness" across different products.
1. Decibel is a logarithmic scale
The human ear's perception of sound is not linear, and sound pressure levels are expressed using a logarithmic scale (decibels). When the sound pressure doubles, the decibel value does not increase by a factor of two, but rather by approximately 6 dB. Therefore, when comparing the loudness of two alarms, it is important to look at the difference in decibels, rather than the original sound pressure value.
II. Reference distance is crucial
The nominal value is often written as "1 m"
Many products are labeled as "97 dB(A) @ 1 m", indicating the sound pressure level at a distance of 1 meter from the device. Field personnel often stand at a greater distance, and sound attenuates with the square of the distance, so the actual loudness at the actual distance will be significantly lower than the labeled value.
The selection should be converted to the on-site distance
If you need to hear clearly at a distance of 3-5 meters, you should calculate the required sound pressure based on this distance, rather than just focusing on the nominal value at 1 meter. When the ambient noise is high, you should also allow for an additional margin above the ambient noise.
III. Weighting Method Affects Listening Perception
A weighting is more akin to the human ear
A-weighting (labeled dB(A)) is commonly seen in daily life and industry, which weights the mid-to-high frequencies and suppresses the low frequencies, making it more similar to the actual auditory perception of the human ear. When looking at parameters, be careful to note whether it is dB(A) or other weightings, to avoid direct comparison with values from different standards.
Peak and duration
Some scenarios focus on instantaneous peak values, while others prioritize continuously audible steady-state sound pressure. For alarm notifications, it is typically assessed whether the steady-state sound pressure level exceeds the background noise level.
IV. Relationship with Other Parameters
The sound pressure level should be considered alongside operating voltage, frequency, and protection level. A device with high sound pressure may still fail if its operating temperature or protection does not meet the site requirements. When selecting a model, it is more prudent to check these factors side by side rather than solely relying on the sound pressure level.
Parameter Table (Concepts Related to Sound Pressure Level)
> The above is a conceptual description. Specific values are subject to the original DIGISOUND documentation. Shanghai Qinuo can assist in verifying the alarm sound pressure, distance, and ambient noise together.
Need selection or documentation for related products?
Tell us the model or application scenario, and we will provide selection advice and technical documentation.