THE BOOM BUDS EAR OCCLUDING EARPHONES

Exceptional stereo earphones for the audiophile enthusiast.

Tight fitting seal - yet comfortable - in the ear canal to block out noise while listening to music.

Standard headphones jack that fits into most music players including
iPods, MP3 players, PC's, CD/DVD players, and PDA's.

Specifications

The Boom Buds are small earphones, which provide environmental noise reduction by effectively occluding the ear canal. Most earbuds, such as those provided with portable music players, are vented to the outside. This improves the ballistics of the speaker driver system and also reduces power consumption. These vents allow environmental noise to enter the ear canals and therefore offer no protection against high-level noise.

The Boom Buds have a solid high impact plastic housing that presents a significant barrier to noise entering the ear canal.

To measure the amount of noise reduction provided in the ear canal, a few simple tests were performed. It is well known that a speaker can also function as a dynamic microphone. In the first part of these tests, this principle is utilized.

Inside an anechoic chamber, white noise is generated by speakers at 100 dBSPL. The Boom Buds are exposed to this noise and the resultant signal from the Boom Bud terminals is measured and recorded on an HP 3566 spectrum analyzer. This is the room noise measurement. It is averaged 100 times and recorded as a power spectrum.

Next, the power spectrum is recorded with the Boom Buds placed in a human ear.

Finally the noise is turned and the noise floor is recorded.

Fig. 1 shows these three power spectrums together on one chart. Notice the space between the Room Noise spectrum and the In Ear Noise spectrum. This space represents the frequency dependant reduction in noise when the Boom Bud is inserted in to the ear. Notice also that at some frequencies, the In Ear Noise is nearly the same as the Noise Floor.



The HP 3566 analyzer allows for computation of ratios between power spectrums. This calculation yields frequency response. In this case the ratio of Room Noise to In Ear Noise is computed. Dividing Room Noise by In Ear Noise yields Noise reduction in ear canal as shown in Fig.2. The highest noise reduction occurs at 2.416 kHz with 39.22dB reduction.



The frequency response of the Boom Buds is measured next. This time the Boom Buds are used as speakers. White noise, generated by the HP3566, is set at 300mV and connected to the Boom Buds. While they are thus energized, a reference microphone is placed near one Boom Bud outlet. The signal from this microphone is recorded as power spectrum. Since it is a comparison of input signal vs. output signal, it can be regarded as a frequency response.



We should expect the ear canal to alter this frequency response when the Boom Bud is inserted. To measure this change, a plastic canal is constructed which has roughly the same dimensions as a human ear canal. The plastic canal is 0.25  diameter and 1.25  long. It is constructed so the reference microphone can be placed where the eardrum would reside. It is also flared out at the other end to accommodate the Boom Bud.

Fig.3 shows the frequency response of the Boom Bud in open air and in the simulated ear canal. Notice the improved low frequency response when the Boom Bud is inserted. Notice also the increased generated sound pressure.

Fig.4 shows the ear canal simulator used in these tests with the Boom Bud and reference microphone in place.



It is understood that all ear canals are different, so the change in response shown above is an approximation.