Acoustical Isolation vs Acoustical Treatment - What is soundproofing? (Part 1)

December 04, 2016 by Fu Yongwei in audio

In the month of December, let's explore some fundamental differences between acoustical isolation and treatments. I'll start off by answering one of the most commonly asked questions, "does sticking acoustic foams on the wall soundproof your room"? The short answer would be no, and we will take the chance to understand why in this blog series.

Acoustic foams (egg crates) on the wall, Credits Aksa Akustik

What is acoustical isolation?

Acoustical Isolation, commonly referred as “sound proofing” by many, is the work needed to help the acoustical space to isolation itself from its environment, usually with the use of insulating barriers. Simply put, acoustical isolation adjusts the effectiveness of keeping any sounds in and out of the room. When evaluating a place, even if the room has excellent acoustical characteristics (e.g. even low-frequency radiation), if external sounds can intrude the space easily, the room will not worth much. Imagine that you're recording a soft passage in your room, but it is always being interrupted with the barking of a neighbour’s dog (a typical scenario in the heartland of Singapore). The dog now governs the whole working process as you must work around it, possibly resulting in a less efficient process.

Difference between insulation vs. isolation

The distinction between insulation and isolation should also be clarified. A given wall construction, for example, will offer a particular transmission loss to sound travelling through it. This absorptive sound transmission will be referred as insulation. On the other hand, isolation is a general term applying to structures. For instance, the difference between the sound pressure level (SPL) taken inside and outside a studio would be a measure of the isolation of the studio itself. Generally speaking, these acoustically sensitive spaces would desire a high isolation index and we would look into that at the later part of the blog.

In the topic of creating a long-term effective and efficient space for any acoustical work, it is frequently being agreed upon that room with a high rejection of intruding / escaping sounds will be preferred. As sound isolation works require some level of structural modifications to the room, it will be impossible (at least for most of us) to execute these structural changes once your system is up. So, if you have the luxury to work on a room from scratch, sound isolation would be your priority.

Good separation across the full audio spectrum would demand heavy walls, decoupled noise sources and other architectural features. Sadly speaking, there isn’t any "one fits all" solution when it comes to acoustic and most calculations would have some level of tolerances between theory and application. Several factors cause these and just to name a few, material differences, craftsmanship and air humidity can affect the accuracy of calculations.

Sound Transmission Class (STC)

The Sound Transmission Class (STC) Standard rates the sound-blocking ability of a material or structure. The STC is a single-number rating of airborne transmission loss measured at sixteen 1/3 octave band (16 divisions) with centre frequencies ranging from 125Hz to 4000Hz. In summary, the higher the STC value, the greater the sound insulation provided. STC is a reasonable simplified (convenient) measurement standard. Although there are differences between iterations (mainly pre 1999) and it account of transmission loss and not frequency, the STC rating is adequate for one to evaluate and make an informed decision on the sound isolation ability in the room. In short, when comparing a wall rated at STC-30 to STC-42, it is quickly evaluated that the STC-42 wall offers 12 dB more transmission loss than the other.

It is without a doubt that every single wall surfaces (e.g. ceiling) can affect the isolation index of the room and how "soundproof" your room will be determined by the weakest link, commonly a "sound leak". To achieve a low noise level in a room, every aspect of the design and construction must be scrutinised. Common leak sources range widely from an unsealed door to window. Simply put, as long as sound can be displaced easily by air, this will exponentially decrease the overall isolation quality even though the rest of the surfaces are treated properly. Hence, it is important to ensure that attention is put on every single surface of the room (don't put all your eggs in one basket) to make sure that the room is properly sealed.

In the next article, we will look at how to survey and evaluate a prospective room.

High CRI Bulb

August 18, 2016 by Fu Yongwei in EDC, tech

This is a follow-up post from my Prometheus Beta-QR EDC flashlight. I have received multiple enquiries regarding the type of light used in this particular flashlight. As some of you have observed in some of the beta-qr review videos on Youtube, you will notice that the light “colour” (temperature) is slightly different from your usual “white colour” flashlight. In this particular case, the beta-qr uses high colour rendering index (CRI) LED rather than the generic “white” LED bulb.

The CRI of a light source is a quantitative measure of its ability to reproduce the colours of different object faithfully in comparison with an ideal or natural light source. To put it simply, CRI lights help objects to display its colours “realistically” or “naturally” as compared to a reference, usually an incandescent bulb. These bulbs have significant improvement to help photographers, videographers to achieve images that have better colour representation when used.

The effects of CRI raitings, Credits Mdidea

To answer the most common question I encountered so far, the light from a High CRI bulb can bring more merits that it looks. Though some High CRI bulb may appear to be dimmer that its generic white LED counterpart, a high-quality CRI bulb is more efficient in its colour representation and will help user / camera sensors to perceive better. Hence, even though some CRI bulb might be spec at a lower lumen rating but its efficiency can far compensate for this shortcoming.

Below are some samples were taken with respect to the different light source, namely, white LED light (Jetbeam PA10), High CRI flash (Nexus 5x) and High CRI light from beta-qr.

High CRI bulb are getting more affordable and manufacturers are starting to include them in their products, e.g. Google Nexus 5x by LG. This is a good development in my opinion, as it can help cameras (even the lower resolution ones) achieve a more flattering and accurate representation of an image. Thus, creating a more holistic balance between camera sensors and light quality. Photography and videography are the art of capturing light and emotion, without a good light source, your highly sensitive camera senses will still be flawed.

In the past, many have avoided the use of LED lights mainly due to this particular reason, namely, bad colour representation. However, high CRI bulbs are creating a viable avenue for many photos and video enthusiast to explore as they are a lot more power efficient and can be very portable (e.g. Prometheus Beta-Qr).

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Buying Inexpensive Earphone / Headphones

August 14, 2016 by Fu Yongwei in audio

It is certain that in the world of audio engineering, many of us have often associate quality audio gear with a high price tag. For instance, when buying a pair of earphones, the most convenient approach (but least objective) would associate the earphones’ performance with its relative price. Personally, I still see the values in economically priced earphones and comparing them with higher end earphones are similar to comparing a commercial vehicle to a sports car, where they are just simply different.

As mentioned in my previous post (Future Proofing Your Technology), it is important to have a realistic idea of what you are going to use earphones with, hence optimizing every single penny spend towards better sonic performances. When it comes to inexpensive earphones, I would prioritize build quality and ease of use of the earphones. Ironically, sonic superiority is the least of my concerns but adequate fidelity should be expected.

When you are looking for a low priced earphone, chances you are also on a budget and would not want to splurge on anything unnecessary. Thus, it is even more important to pay attention to the build quality of the device in order to ensure the longest possible service life from your earphones. This allows you to save up and possibly have the financial resources available for an upgrade in the future. It would be inequitable to expect inexpensive earphones to possess features such multi-core to single conductor cables to improve the signal to noise ratio (SNR). A more pragmatic perspective would be to analyse the durability of the earphones. Some earphones are built extremely sturdy, for example, being able to withstand cable stresses experienced during sports workout and being washable (water resistance) to rinse off any excessive sweat or dust. A notable example would be the Sennheiser sports series earphones that range below $100 SGD.

In addition, replaceable parts are often another strong suit to help extend the serviceability of the earphones. There are many variations from replaceable ear tips (foams) to headbands, but the one I find it most appealing would be the detachable and replaceable cables. If you have been an audio junkie like myself, you would have notice that for the most part of your listening experiences, the cables in your earphones are the ones that stop working first. Unless you favour the DIY approach where you can re-solder the connections yourself, many would just discard an otherwise still functioning speaker drivers.

My 5 years old AKG K451 headphone would only last this long thanks to replaceable cables.

The next criteria require a little bit of effort but it will save you from many unnecessary hassles and spending. When you’re on a budget, the only items you should invest in (assuming that you already have a functioning media playback device) are your earphones and nothing else. Do not be tempt by other additional accessories such as a portable audio amplifier, where it claims to help enhance sonic characteristic. Most playback devices have an output impedance that are at kilo ohms ranges and that is sufficient to drive most earphones with an impedance of 160 ohms and below (assuming output impedance of your playback device is 10K ohms). Introducing additional audio amplifier along the circuit will be futile as it does not help optimize your signal chain.

Beyerdynamic MXP 50 iE, a very popular budget earphones (46Ω), Credits Beyerdynamic

To conclude, inexpensive earphones are still very relevant, even to an audio enthusiast, it serves as a temporary option for one to save up and upgrade. Fortunately, there are many prospective earphones that are right below the $150 SGD mark where it will comfortably suffice the requirements mentioned above. Have reasonable expectations and these earphones might be applicable to your daily listening needs.

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