Use a sound pressure level meter. But don't forget to mention the distance when you write down the value in decibels.
The more far away you are from the horn the lower is the measured level.
A dB value without the distance is useless.
For example, the UL standard for smoke alarms is 85 dB at 10 feet.
The loudness of a shout or sound pressure level is found by this form: ptotal = p0 + posc ..where... p0 = local ambient pressure posc = sound pressure deviation
Compare Sound power, Sound pressure, and Sound intensity. All share as level the same unit of measure: the decibel (dB). The term "sound level" is commonly substituted for each. As characteristic impedance of air we use the round value Z = 400 N·s/m³ (Pa·s/m). Then the "sound level", that is the sound pressure level Lp and the sound intensity level LI is exactly the same as a decibel value. The sound power or acoustic power is the sound energy constantly transferred per second from the sound source. A sound source has a given constant sound power that does not change if it is placed in a different room environment. Sound power is a theoretical value that is not measurable. It is calculated and expressed in watts and as sound power level LW in decibels. A sound source produces sound power and this generates a sound pressure fluctuation in the air. Sound power is the distance independent cause of this, whereas sound pressure is the distant-dependent effect.
The unit of measurement for sound pressure level is decibels (dB).
Usually sound pressure level (SPL) in decibels (dB) is meant. A sound level meter is an instrument which measures the sound pressure level. The reading from a sound pressure level meter (SPL meter) does not correlate well to human-perceived loudness.
Sound power level (in decibels) is calculated by determining the sound pressure level (in decibels) at a reference distance from the source of the sound. The sound power level is based on the sound pressure level and the distance from the source, using the inverse square law to account for the spreading of sound waves in three dimensions.
The sound pressure level of a 100 dB siren is 100 times greater than that of an 80 dB alarm clock. Most people would perceive the 100 dB siren to be around twice as loud compared to the 80 dB alarm clock due to the logarithmic nature of the decibel scale and human perception of sound intensity.
The volume of a sound is measured by the sound pressure in pascals or newtons per square meter. The sound pressure level is measured by a sound pressure level meter (SPL meter).
Sound power or sound intensity I is a sound energy quantity.Sound pressure p is a sound field quantity.Sound intensity is sound pressure squared. I = p².See related link.
A SPL meter is a sound pressure level meter where a microphone diaphragm is moved by the sound pressure variations and the voltage output of the microphone is shown at a voltmeter. The volts are calibrated to decibels.
The volume of a sound is measured by the sound pressure in pascals or newtons per square meter. The sound pressure level is measured by a sound pressure level meter (SPL meter).
Sound pressure level measures the intensity of sound at a specific point, while sound power level measures the total sound energy produced by a source. Sound pressure level is a measure of how loud a sound is perceived, while sound power level is a measure of the total energy output of a sound source. In terms of measuring sound intensity, sound pressure level is often used to determine the impact of sound on a specific location, while sound power level is used to quantify the overall output of a sound source.
Sound power level refers to the total amount of sound energy produced by a source, measured in watts. Sound pressure level, on the other hand, measures the intensity of sound waves at a specific point, typically in decibels. In the context of measuring sound intensity, sound power level is the source of the sound, while sound pressure level is the measurement of how loud the sound is at a particular location. The two are related in that sound power level influences sound pressure level, but they are distinct measurements that provide different information about the sound being produced.